How to activate and use civil defence shelters Internal security | Publications of the Ministry of the Interior 2026:3 Ministry of the Interior www.intermin.fi PO Box 26, FI-00023 Government General guide How to activate and use civil defence shelters General guide Ira Pasi (editor) Ministry of the Interior Helsinki 2026 Finland Publications of the Ministry of the Interior 2026:3 Publication distribution Institutional Repository for the Government of Finland Valto julkaisut.valtioneuvosto.fi Ministry of the Interior CC BY-SA 4.0 ISBN pdf: 978-952-324-655-3 ISSN pdf: 2490-077X Layout: Government Administration Department, Publications Helsinki 2026 Finland https://julkaisut.valtioneuvosto.fi/ Description sheet 21 January 2026 How to activate and use civil defence shelters General guide Publications of the Ministry of the Interior 2026:3 Subject Internal security Publisher Ministry of the Interior Editor Ira Pasi Group author Ministry of the Interior Language English Pages 73 Abstract The guide on how to activate and use civil defence shelters has been prepared as part of the project Self-preparedness for emergency conditions. The project was funded by the Fire Protection Fund. The guide aims to support the preparation of a plan for the activation and use of a civil defence shelter and to increase the parties’ competence related to civil defence shelters. The guide contains the basics of activating and using a civil defence shelter and its planning. The guide is based on regulatory obligations. The guide contains voluntary, alternative and proven practices and recommendations for fulfilling the obligations. Good practices and recommendations are voluntary courses of action, and they are not absolute in any respect, unlike statutory obligations. Section 2(2) of the government decree on rescue services (407/2011) requires that the rescue plan explain how independent preparedness is implemented in emergency conditions. Planning the activation and use of a civil defence shelter is part of the preparation of a rescue plan. Pursuant to section 76 of the Rescue Act (379/2011), it must be possible to activate a civil defence shelter within 72 hours. In order for the activation of a civil defence shelter to succeed within this time and the shelter to be used as intended, if necessary, the activation and use of the civil defence shelter must be planned in advance. Keywords civil defence shelters, civil defence, emergency plan, security, independent preparedness, internal security ISBN PDF 978-952-324-655-3 ISSN PDF 2490-077X Reference number VN/740/2024 Project number SM001:00/2024 URN address https://urn.fi/URN:ISBN:978-952-324-655-3 https://urn.fi/URN:ISBN:978-952-324-655-3 Kuvailulehti 21.1.2026 Väestönsuojan käyttöönotto ja käyttö Yleisopas Sisäministeriön julkaisuja 2026:3 Teema Sisäinen turvallisuus Julkaisija Sisäministeriö Toimittaja Ira Pasi Yhteisötekijä Sisäministeriö Kieli englanti Sivumäärä 73 Tiivistelmä Väestönsuojan käyttöönotto ja käyttö -yleisopas on laadittu osana Omatoiminen varautuminen poikkeusoloihin -hanketta. Palosuojelurahasto rahoitti hanketta. Oppaan tavoitteena on tukea väestönsuojan käyttöönotto- ja käyttösuunnitelman laatimisessa sekä lisätä toimijoiden väestönsuojiin liittyvää osaamista. Opas sisältää perusteet väestönsuojan käyttöönotosta ja käytöstä sekä sen suunnittelusta. Opas perustuu säädöksissä asetettuihin velvoitteisiin. Opas sisältää vapaaehtoisia sekä vaihtoehtoisia ja hyväksi todettuja käytäntöjä ja suosituksia velvoitteiden toteuttamiseksi. Hyvät käytännöt ja suositukset ovat vapaaehtoisia tapoja toimia, eivätkä ole miltään osin ehdottomia, toisin kuin säädösten velvoitteet. Pelastustoimesta annetun valtioneuvoston asetuksen (407/2011) 2 §:n 2 momentissa velvoitetaan selvittämään pelastussuunnitelmassa, miten omatoiminen varautuminen toteutetaan poikkeusoloissa. Väestönsuojan käyttöönoton ja käytön suunnittelu on osa pelastussuunnitelman laatimista. Pelastuslain (379/2011) 76 §:n mukaisesti väestönsuoja on voitava ottaa käyttöön 72 tunnissa. Jotta väestönsuojan käyttöönotto onnistuu tässä ajassa ja suojaa voidaan tarvittaessa käyttää sille tarkoitetulla tavalla, väestönsuojan käyttöönotto ja käyttö on suunniteltava etukäteen. Asiasanat väestönsuojat, väestönsuojelu, pelastussuunnitelmat, turvallisuus, omatoiminen varautuminen, sisäinen turvallisuus ISBN PDF 978-952-324-655-3 ISSN PDF 2490-077X Asianumero VN/740/2024 Hankenumero SM001:00/2024 Julkaisun osoite https://urn.fi/URN:ISBN:978-952-324-655-3 https://urn.fi/URN:ISBN:978-952-324-655-3 Presentationsblad 21.1.2026 Ibruktagande och användning av skyddsrum Allmän guide Inrikesministeriets publikationer 2026:3 Tema Inre säkerhet Utgivare Inrikesministeriet Redigerare Ira Pasi Utarbetad av Inrikesministeriet Språk engelska Sidantal 73 Referat En allmän guide om ibruktagande och användning av skyddsrum har utarbetats inom projektet Egen beredskap för undantagsförhållanden. Projektet finansierades av Brandskyddsfonden. Syftet med guiden är att stödja utarbetandet av en plan för ibruktagande och användning av skyddsrum och öka aktörernas kompetens i fråga om skyddsrum. Guiden innehåller grundläggande information om ibruktagande och användning av skyddsrum och om planeringen av detta. Guiden bygger på lagstadgade skyldigheter. Den innehåller frivillig, alternativ och beprövad praxis och rekommendationer för att uppfylla skyldigheterna. God praxis och rekommendationer är frivilliga att följa och är inte ovillkorliga, till skillnad från de lagstadgade skyldigheterna. Enligt 2 § 2 mom. i statsrådets förordning om räddningsväsendet (407/2011) ska räddningsplanen innehålla en redogörelse för hur egen beredskap genomförs i undantagsförhållanden. Planeringen av ibruktagandet och användningen av skyddsrum ingår i utarbetandet av räddningsplanen. Enligt 76 § i räddningslagen (379/2011) ska skyddsrum kunna tas i bruk inom 72 timmar. För att skyddsrummet ska kunna tas i bruk inom utsatt tid och vid behov kunna användas på avsett sätt, ska ibruktagandet och användningen av skyddsrummet planeras på förhand. Nyckelord räddningsplan, säkerhet, egen beredskap, säkerhetsplanering, räddningsplanering, inre säkerhet ISBN PDF 978-952-324-655-3 ISSN PDF 2490-077X Ärendenummer VN/740/2024 Projektnummer SM001:00/2024 URN-adress https://urn.fi/URN:ISBN:978-952-324-655-3 https://urn.fi/URN:ISBN:978-952-324-655-3 Contents FOREWORD.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1 Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.1 Purpose of the guide.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2 Obligation to plan the activation and use of a civil defence shelter.. . . . . . . . . . . . . . . . . . . . . . 12 2 Background information on civil defence shelters.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.1 Working principle of civil defence shelters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Order to activate civil defence shelters.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3 Who are civil defence shelters intended for?.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.4 Alerting and protecting the population. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5 What should those going to the shelter consider?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3 Preparing a plan for the activation and use of the civil defence shelter.. . . . . . . . . . . . . . 23 3.1 Responsibility for drawing up and updating the plan.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2 Content of the plan.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.3 Documentation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.4 Updating the plan.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4 Preparation for the activation of a civil defence shelter.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.1 Basics of activation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.2 Organisation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.3 Material preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.4 Activation tasks.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.4.1 Emptying and preparing the space.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4.4.2 Construction and outfitting.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 4.4.3 Commissioning of technical systems.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5 Preparations for protection and the use of the civil defence shelter.. . . . . . . . . . . . . . . . . . . . 44 5.1 Division of tasks during sheltering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 5.2 Moving to a civil defence shelter.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.3 Modes of use of civil defence shelters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.3.1 Standby mode.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.3.2 Bypass operation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 5.3.3 Closed operation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 5.3.4 Filtration operation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5.4 Instructions for staying in a civil defence shelter.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5.5 Preparing for problems and dangers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 6 Communicating about the plan for the activation and use of the civil defence shelter and familiarising the parties concerned.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 7 Supervision and guidance relating to shelters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.1 Supervision by the rescue authorities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.2 Guidance and advice provided by the rescue department. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Appendix 1: Glossary and key concepts.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Appendix 2: Materials and supplies of a civil defence shelter.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Sources.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8 Publications of the Ministry of the Interior 2026:3 F O R E W O R D The Ministry of the Interior set up the project Independent preparedness for emergency conditions to prepare instructions on 4 March 2024 (VN/740/2024). The term of the project is from 1 March 2024 to 31 June 2026. The project prepared three general guides titled Emergency plan, How to activate and use civil defence shelters, and How to maintain and inspect civil defence shelters. The project was funded by the Fire Protection Fund. The project contributed to implementing the Government Programme entry on strengthening individual emergency planning competence in all population groups, for example through guidance, counselling and supervision. The objective of the project was to clarify the obligations laid down in legislation and to harmonise different actors’ operating models relating to emergency planning and civil defence shelters while also addressing needs for communication. A steering group and a working group were set up for the project, as well as three divisions, one for each set of instructions. The Management Group of the Ministry of the Interior Department for Rescue Services served as the steering group of the project. The project working group consisted of experts from the Ministry of the Interior Department for Rescue Services. The Ministry of the Interior was responsible for preparing the instructions. Project Manager Ira Pasi from the Ministry of the Interior Department for Rescue Services was the rapporteur responsible for preparing the project. A division was established for each set of instructions, the task of which was to provide expert assistance and ensure that the different actors’ viewpoints were incorporated in the guides. Working group Chair: Kirsi Rajaniemi, Ministerial Adviser, Ministry of the Interior, Department for Rescue Services Pasi Ryynänen, Director of Unit, Ministry of the Interior, Department for Rescue Services Jussi Korhonen, Director, Civil Preparedness, Ministry of the Interior, Department for Rescue Services Jarkko Häyrinen, Senior Rescue Officer, Ministry of the Interior, Department for Rescue Services Ira Pasi, Project Manager, Ministry of the Interior, Department for Rescue Services 9 Publications of the Ministry of the Interior 2026:3 Division on activating and using civil defence shelters Chair Jarkko Häyrinen, Senior Rescue Officer, Ministry of the Interior, Department for Rescue Services Senior Fire Inspector Susanna Rautio, Southwest Finland Emergency Services Head of Preparedness Juha Alander, Eastern Uusimaa Fire and Rescue Services Senior Teacher Petri Huttunen, Emergency Services Academy Finland Chief Economist Jukka Kero, Finnish Real Estate Federation MLaw Sara Rintamo, Finnish Real Estate Management Association Pertti Heikkilä, Specialist, Finnish National Rescue Association Trainer Janne Rahunen, North Karelia Rescue Association Head of Preparedness Katja Ahola, Finnish Association of Fire Officers Martin Mitikka, Väestönsuojien tarkastajat ry Pekka Rajajärvi, Counsellor of Construction Secretary: Ira Pasi, Project Manager, Ministry of the Interior, Department for Rescue Services The draft guide was circulated for comments between 12 June and 11 August 2025 on lausuntopalvelu.fi. In total, 37 statements were received. Tanja Mannila and specialists from the Ministry of the Interior Department for Rescue Services contributed their expertise to the preparation of the guide. In the preparation phase of the guide, experts from different fields, parties working with civil defence shelters, rescue departments and representatives of the Finnish Disability Forum were consulted across a broad front. I would like to extend my warmest thanks to all those who participated in the project and in the preparation of the guide! Helsinki, November 2025 Ira Pasi Project Manager, Ministry of the Interior Rescue Department 10 Publications of the Ministry of the Interior 2026:3 1 Introduction Section 2(2) of the government decree on rescue services (407/2011) requires that the rescue plan explain how independent preparedness is implemented in emergency conditions. Planning the activation and use of a civil defence shelter is part of the preparation of a rescue plan. Civil defence aims to protect the civilian population against the dangers of hostilities and accidents and help the population cope with the immediate effects of hostilities and create the necessary conditions for survival. Activities related to civil defence include, for example, warning the population, evacuation, sheltering in civil defence shelters, and firefighting and rescue operations. According to Additional Protocol (I) to the Geneva Convention (82/1980, Chapter VI, Article 66), the international emblem of civil defence is a blue equilateral triangle on an orange background, which is shown in Figure 1. Figure 1.  The civil defence symbol, which is a blue equilateral triangle on an orange background, also marks civil defence shelters. 11 Publications of the Ministry of the Interior 2026:3 Civil defence shelters are designed for wartime use and are an important part of civil defence as a whole. Civil defence shelters have been built in Finland since the 1930s, and they are a natural part of the built environment. Civil defence shelters are built in connection with larger buildings, i.e., where the need for protect the population is greatest and there are many people. Civil defence shelters are often built in blocks of flats, terraced houses, schools, hospitals, shopping centres, office buildings and other public and private buildings. Pursuant to section 76 of the Rescue Act (379/2011), it must be possible to activate a civil defence shelter within 72 hours. In order for the activation of a civil defence shelter to succeed within this time and the shelter to be used as intended, if necessary, the activation and use of the civil defence shelter must be planned in advance. It is also important to see to the maintenance of civil defence shelters. The rescue plan must determine how independent preparedness is implemented in emergency conditions (section 2(2) of the government decree on rescue services). Thus, the plan for the activation and use of the civil defence shelter is planned as part of the site’s rescue plan. The drawing up of the emergency plan is the responsibility of the occupant or holder of the building or the site (Rescue Act 15(1)). Civil defence shelters are not the only way to protect the population. Other means of protection include the population’s independent moving to safer areas, authority-effected population evacuation, sheltering indoors and building temporary civil defence shelters. Various protection methods are presented in Figure 2. The most appropriate method for protecting the population is used. Figure 2.  In addition to taking shelter in civil defence shelters, means of protecting the population against wartime weapons effects include the population’s independent moving to safer areas, authority-effected population evacuation, sheltering indoors and building temporary civil defence shelters. SCHOOL STORE 12 Publications of the Ministry of the Interior 2026:3 In emergency conditions, when sheltering against weapons effects, people seek shelter in the nearest civil defence shelter or by structures that are as strong as possible, such as the central parts of a building. In a protection situation, there is very little time between the warning and the danger, and at that time one must avoid movement outdoors and protect oneself quickly. 1.1 Purpose of the guide The purpose of the guide is to support the preparation of a plan for the activation and use of the civil defence shelter. The guide does not comment on the detailed solutions of civil defence shelters, as they vary from site to site. The guide is based on regulatory obligations. The guide contains voluntary, alternative and proven practices and recommendations for fulfilling the obligations. Good practices and recommendations are voluntary courses of action, and they are not absolute in any respect, unlike statutory obligations. The guide aims to take all civil defence shelters into account at a general level, regardless of their size and protection class. The main target group of the guide is building holders, owners and operators, actors providing services for these parties, the users of the civil defence shelters and rescue authorities. The guide was prepared as part of the Independent preparedness for emergency conditions project. Three guides were produced in this project, titled “Rescue plan”, “How to maintain and inspect civil defence shelters” and “How to activate and use civil defence shelters”. The project was funded by the Fire Protection Fund. 1.2 Obligation to plan the activation and use of a civil defence shelter Provisions on drawing up a rescue plan are laid down in section 15 of the Rescue Act. Section 1 of the government decree on rescue services specifies the buildings and other sites for which a rescue plan must be drawn up. The obligation to draw up a rescue plan applies, among other things, to residential buildings with at least three dwellings, schools, shopping centres and shops of over 400 square metres of floor space, workplaces of at least 50 workers and care facilities, accommodation establishments, churches, libraries, etc. However, not all of these sites necessarily have a civil defence shelter. 13 Publications of the Ministry of the Interior 2026:3 The rescue plan is a description of the site’s independent preparedness in accordance with section 14 of the Rescue Act, which includes, among other things, preparing for protecting persons in hazardous situations. The rescue plan must also determine how independent preparedness is implemented in emergency conditions (407/2011 2(2)). Government proposal for the Rescue Act (HE 257/2010 vp) notes that independent preparedness for emergency conditions includes preparedness for site-specific civil defence measures, including the activation and use of civil defence shelters on the site under emergency conditions. In armed conflicts, action at the site in emergency conditions means, for example, taking shelter in a civil defence shelter and operating it. Therefore, if the property has a civil defence shelter, a plan for the deployment and use of the civil defence shelter must be drawn up as part of rescue planning. However, it is also necessary to plan how the civil defence shelter will be activated and how it will be used at sites where no rescue plan is required. The plan should be drawn up in writing. As the obligation to plan the activation and use of a civil defence shelter is included in the obligation to prepare a rescue plan, the same party is also responsible for drawing up the rescue plan, i.e., the holder of the building or site. 14 Publications of the Ministry of the Interior 2026:3 2 Background information on civil defence shelters 2.1 Working principle of civil defence shelters Most civil defence shelters are property-specific civil defence shelters, which are built in connection with the construction of the building, when the building size is large enough. Common civil defence shelters may also be built for several buildings. The buildings, and thus also civil defence shelters, may be owned by private or public bodies. In addition, public civil defence shelters have been built in some towns to protect the mobile population and to supplement the need for shelter places. Finnish civil defence shelters are designed to provide protection against effects of weapons, collapsing buildings, ionising radiation and toxic substances (section 74 of the Rescue Act). Further provisions on factors affecting the protection capacity of civil defence shelters, such as civil defence shelter structures, devices, supplies and maintenance, are laid down in the decrees of the Government and the Ministry of the Interior. 15 Publications of the Ministry of the Interior 2026:3 Figure 3.  Civil defence shelters provide protection from the effects of weapons, collapsing buildings, ionising radiation and toxic substances. The regulations concerning the construction of civil defence shelters, devices and supplies have changed over time, which is why civil defence shelters built at different times differ somewhat from each other in terms of their structure and equipment. Civil defence shelters built in the 1960s and early 1970s have, among other things, a different ventilation device than modern ones. Figure 4 shows ventilation equipment in a civil defence shelter from the 1960s and 1990s. In addition, the protective equipment, such as water tanks, have varied from decade to decade. Hätäpoistumisreittiä voidaan käyttää, jos rakennus sortuisi. Väestönsuojaan sisään otettava ilma voidaan suodattaa myrkyllisiltä kaasuilta ja radioaktiivisilta aineilta. Vahvat rakenteet suojaa asevaikutuksilta kuten paineaalloilta ja sirpalevaikutuksilta. Väestönsuojan varusteet parantaa suojautumisen olosuhteita ja mahdollistaa pidemmän oleskelun suojassa. The emergency escape route can be used if the building were to collapse. A civil defence shelter’s supply air can be �ltered from toxic gases and radioactive substances. Strong structures protect against the e�ects of weapons, such as blast waves and fragments. A civil defence shelter’s equipment improves the conditions for sheltering and enables longer stays in the shelter. 16 Publications of the Ministry of the Interior 2026:3 Figure 4.  The devices of civil defence shelters built at different times may have different appearances, but the operating principle is the same. The figure shows the ventilation equipment for category C civil defence shelters built in the 1960s on the left and category S1 civil defence shelters built in the 1990s on the right. (Figures: Ministry of the Interior) There are very different sizes of civil defence shelters, which can have shelter places ranging from a few dozen to several thousand people. The technology of large civil defence shelters differs slightly from that of smaller reinforced concrete shelters, and operating their technology requires special expertise. Despite the differences, the operating and protection principle of civil defence shelters has remained unchanged in Finland throughout the history of the construction of civil defence shelters. All civil defence shelters share in common that, thanks to their strong structures, they can withstand conventional arms impacts well, including the collapse of the building on top of the civil defence shelter. 17 Publications of the Ministry of the Interior 2026:3 Civil defence shelters usually have at least two independent exit routes with reinforced structures. Civil defence shelters built underground also have a separate emergency exit route through which one can leave the shelter even if the building had fallen on top of the civil defence shelter. An exception to this are lightweight civil defence shelters of less than 20 m2, built 1991–1999. A civil defence shelter has its own ventilation device, which works also without electricity. The ventilation device allows for filtering the air entering the shelter from toxic gases or radioactive substances if necessary. In addition to the ventilation device, the ventilation system of a civil defence shelter includes a distribution duct through which the air is distributed evenly into the shelter space and relief valves through which the air is led out of the shelter space. The ventilation for normal- conditions use is closed tightly with shut-off flanges in connection with activation. Other key civil defence shelter structures and equipment include a sewer shut- off valve, which can also be used to seal the sewer in the space airtight, and an overpressure gauge that can be used to monitor how much overpressure there is in the shelter. A technical system that enables the use of telephones and other communication devices is also an important part of civil defence shelter equipment. A civil defence shelter must have different equipment and supplies that improve the conditions for sheltering and enable longer stays in the shelter. These include reserve water tanks and dry toilet units. There is no obligation to stock food, for example, in a civil defence shelter. 2.2 Order to activate civil defence shelters The authorities will issue instructions in advance on preparedness and preparation in situations where the security policy situation in Finland has become more stringent. The authorities will provide guidance on how to improve independent preparedness. It is important to follow the instructions of the authorities. A civil defence shelter must be made ready to use if the rescue authority of the Ministry of the Interior or the wellbeing services county orders that civil defence shelters be prepared for use under section 36 of the Rescue Act. Pursuant to section 76 of the Rescue Act, civil defence shelters, equipment and devices shall be kept in such a condition that the civil defence shelters can be activated within 72 hours. When a civil defence shelter has been prepared for use once and left in standby 18 Publications of the Ministry of the Interior 2026:3 mode, it can then be used for rapid sheltering. An effort will be made to issue an official regulation on preparing civil defence shelters for use for use as early as possible. A civil defence shelter can be prepared for use in accordance with the decisions of the owner or holder of the shelter, even without a separate order, for example in situations where the Finnish security policy situation has become more stringent. Measures related to the activation of civil defence shelters may also concern the property of parties other than the owner of the building or affect the rights of others. For this reason, before independent activation, it must be ensured, for example, that the owner has the right to interrupt the tenant’s normal-conditions use of the premises of the civil defence shelter or to transfer property in the civil defence shelter, or that there are no obstacles to excavating the exit of the emergency escape route, or that it does not complicate other functions. 2.3 Who are civil defence shelters intended for? Civil defence shelters built in or near a building are designed for the use of those living, working or otherwise spending time in the building (section 71 of the Rescue Act). However, any person in need of shelter may take shelter in a civil defence shelter if they do not endanger the safety of other persons in the shelter. Under the Geneva Convention (Treaty Series of the Statute Book of Finland 8/1955) and its Additional Protocol (I) (82/1980, Art. 51, 58, 61–67) and the Universal Declaration of Human Rights (UN General Assembly, 1948, Art. 3) persons must be admitted to a civil defence shelter as long as there is room there. Civil defence shelters are designed for the use of persons living, working or otherwise spending time in the building. However, any person in need of shelter may take shelter in a civil defence shelter if they do not endanger the safety of other persons in the shelter. In actual sheltering situations, there is very little time between the alarm and the actual danger. In most cases, the civil defence shelter is located in the same building as its intended users, which means that sheltering is quick. Based on the sufficiency of ventilation, each civil defence shelter is rated for a certain number of persons. For this reason, when using a civil defence shelter, it must be known how many persons the civil defence shelter is rated for. In a real 19 Publications of the Ministry of the Interior 2026:3 situation, the maximum number of people can be deviated from, for example, when the ventilation of a civil defence shelter is in bypass operation, in which case the air in the shelter changes well. Civil defence shelters are intended for sheltering people. Guide and assistance dogs serve as aids for their users, and their presence is essential for the safety of their users. Access of guide and assistance dogs to civil defence shelters with their assisted person promotes effective equality (section 9 of the Non-Discrimination Act 1325/2014). Pets are sheltered indoors, for example dwellings in buildings. 2.4 Alerting and protecting the population Under section 36(1)(1) of the Rescue Act, a rescue authority of the Ministry of the Interior or of a wellbeing services county may order people to take shelter. In emergency conditions, once civil defence shelters have been activated, one may always take shelter in them according to one’s own assessment without a separate exhortation or order from the authorities. One may also leave a civil defence shelter if one so wishes, provided that that does not compromise the safety of other persons in the shelter. Information on a danger threatening the population and its end is provided to the population through the authorities’ warning systems, i.e., the alarm system (sirens) and emergency warnings. If there was a threat of armed aggression against Finland and civil defence shelters had been ordered to be prepared for use, a general hazard signal is used as a sign of the need to take shelter in a civil defence shelter. The alarm devices are primarily located where people live or move most. It should be noted that in addition to direct weapons impacts, one must protect oneself against shrapnel, which is why one must avoid roaming outdoors and take shelter quickly in a sheltering situation. When sheltering, one must go to the nearest civil defence shelter or indoors, protected by as strong structures as possible, such as the central parts of a building (Figure 5). 20 Publications of the Ministry of the Interior 2026:3 Figure 5.  When taking shelter, go immediately to the nearest civil defence shelter or indoor space protected by maximally strong structures, for example in the middle of a building. The authorities use several different methods to communicate danger. The general alarm signal is a regularly rising and falling sound lasting for one minute, or a warning issued using loudspeakers. The all clear signal is a continuous sound lasting for one minute. It indicates that the threat or danger has passed. In a protection situation, it should be noted that the population alarm system is primarily intended to warn those moving outdoors, and the acoustic signal may not be heard indoors. In addition, the population alarm system does not cover all areas. An all clear signal by siren may not be at all audible inside a civil defence shelter when sheltered. If a general alarm signal is sounded, it will always be accompanied by an emergency warning issued by an authority. The easiest way to obtain information about dangerous situations is to download the 112 Suomi mobile application, which relays hazard and official notifications to the mobile phone. The application is also used in normal conditions for communicating about regional hazards. It is recommended to download the application to all mobile phones, whereby information about a danger is most likely to reach as many people as possible. The application is permitted to track location and send notifications. The emergency announcement is read on the radio and displayed on teletext page 112 and, if necessary, also on the television as text scrolling at the top of the screen. In addition, emergency announcements are published through the Yle application. The purpose of the emergency warning is to warn the public about a hazardous incident and to give them instructions. When the danger no longer exists, a new announcement (all clear) will be issued on the same channels. STORE SCHOOL SPORT 21 Publications of the Ministry of the Interior 2026:3 An emergency announcement is also used to issue instructions if the ventilation device in a civil defence shelter must be prepared for filtration operation, for example in a situation that requires sheltering in a civil defence shelter and, at the same time, a danger caused by dangerous substances or radiation is a threat. 2.5 What should those going to the shelter consider? When the warning comes, use the nearest civil defence shelter. If a civil defence shelter cannot be reached within a few minutes, shelter must be taken indoors under the protection of the strongest possible structures. The protection period may vary from a few minutes to a few hours. Sometimes it may be necessary to stay in the shelter for longer periods of time and also overnight. The need for taking shelter may be repeated several times a week or even several times a day. In emergency conditions, it is always necessary to carry at least an identity card, essential personal medicinal products and a small amount of cash and drinks. Water is reserved for shared use in civil defence shelters. It is also advisable for everyone to reserve personal supplies in advance, which can be grabbed quickly when going to a civil defence shelter. Such supplies include: y food and drink intended for personal use that can be consumed without heating (no alcohol) y personal hygiene supplies y supplies for overnighting and staying in the shelter (e.g. sleeping bags and mattresses) y a headlamp or torch operating on batteries or otherwise without mains power y backup power supply for charging mobile phones and other devices y ear plugs and sleep mask y entertainment (books, games, toys, paper, pens). 22 Publications of the Ministry of the Interior 2026:3 Figure 6.  Goods to be taken to the civil defence shelter and items always carried on person. In terms of the safety and comfort of the use of civil defence shelters, it is important that no alcohol, drugs, weapons, heat-producing devices (e.g., camping stoves or storm lanterns) or products with a strong fragrance are brought into the shelter. CHOCOLATE TAKE WITH YOU ALWAYS WITH YOU XXXXX 23 Publications of the Ministry of the Interior 2026:3 3 Preparing a plan for the activation and use of the civil defence shelter 3.1 Responsibility for drawing up and updating the plan Pursuant to section 15 of the Rescue Act, the drawing up of the emergency plan is the responsibility of the occupant or holder of the building or the site. If more than one operator operates in a building, the holder of the building must draw up the emergency plan in cooperation with the operators. As the obligation to plan the activation and use of a civil defence shelter is included in the obligation to prepare a rescue plan, the same party is also responsible for drawing up the rescue plan. Civil defence shelters have been built in Finland as property-specific shelters, joint civil defence shelters and general civil defence shelters. The building owner is responsible for planning the activation and use of a property-specific civil defence shelter. Properties are jointly responsible for planning the activation and use of a joint civil defence shelters, whereby a joint section on the civil defence shelter will be prepared for the rescue planning of each property. The owner of a general civil defence shelter is usually a municipality, whereby the planning and implementation of the activation and use of the civil defence shelter is the responsibility of the owner, such as the municipality. 3.2 Content of the plan The plan for activation and use is a description of how preparations have been made at the site for the activation and use of the civil defence shelter, and it contains practical instructions for the activation and use of the shelter. The plan also contains safety instructions for those in the shelter and operating instructions for accidents, hazards and disturbances. The planning of the activation and use of a civil defence shelter begins by familiarising oneself with the civil defence shelter of the building and its operating principle. Based on the introduction, it is possible to assess the readiness to activate a civil defence shelter, the possibilities of the sheltered persons to protect themselves and the kinds of hazardous situations that can arise during the sheltering. 24 Publications of the Ministry of the Interior 2026:3 The readiness to activate a civil defence shelter depends on the maintenance practices of the shelter, its technical condition, the adequacy and condition of materials and supplies, and the competence of the users of the property. The possibility for protection include the functional capacity and mobility of persons and the capability to obtain information about a an imminent threat and moving to a civil defence shelter. Dangerous situations occurring during sheltering may include power cuts, accidents, fires in or outside the civil defence shelter in the vicinity of the air intake and a radiation situation. In addition, preparations must be made for the collapse of the building and, consequently, the use of an emergency exit route. Figure 7 presents examples of factors that should be taken into account when preparing the plan for the activation and use of a civil defence shelter. Figure 7.  Example of factors to be taken into account when preparing the plan for the activation and use of a civil defence shelter. The familiarisation with the civil defence shelter and the assessment performed yield an idea of potential problem areas and the aspects that should be given special attention in planning. The planning process may also reveal faults and shortcomings in the functioning of civil defence shelter devices or technology, for example. The shortcomings must be rectified in order to enable the activation and use of the shelter. A plan for the activation and use of the civil defence shelter will be drawn up on the basis of the planning work. Preparation for the activation of a civil defence shelter includes a description of the organisation to be carried out at the time of the implementation of the plan, material preparedness to be carried out in advance and the measures required by the implementation of the civil defence shelter- specific guidelines. More information on preparing for the activation of a civil defence shelter is provided in section 4 of the guide. Sheltering • Communication of danger • Access to civil defence shelter • Special groups’ needs Hazard situations • Power outages • Fires • Need for first aid • Radiation situation • Building collapse Technical characteristics and supplies of the civil defence shelter Issues to be taken into account in the planning of activation and use 25 Publications of the Ministry of the Interior 2026:3 Preparing for the use of a civil defence shelter includes, among other things, a description of moving to a civil defence shelter and the division of duties during sheltering, as well as instructions on the use of the civil defence shelter at different stages of sheltering. An essential part of the use of a shelter is also providing instructions to the persons in it and preparing for accidents, hazards and disruptions. More details on preparing for sheltering and the use of civil defence shelters is provided in section 5 of the guide. 3.3 Documentation The plan for the activation and use of the civil defence shelter is part of the site’s rescue plan, but it can and should often be prepared as a separate document. This can facilitate the maintenance of documents and clarify the communication related to them. The location of a civil defence shelter is public information, but the plan for the activation and use of the civil defence shelter, as well as the rescue plan, does not need to be publicly available to everyone. Above all, the plan is a tool for activating and using a civil defence shelter, and when distributing the plan, it is advisable to take into account and prevent the possibility of using the data for criminal or other inappropriate purposes. However, information related to civil defence shelters must be available at least to those who participate in the maintenance, activation and use of the civil defence shelter or their planning. In addition, the rescue authority has the right to receive the information from the site’s rescue plan it needs to carry out the supervision task, including the planning of the activation and use of the civil defence shelter. It must be possible to present the plan for activation and use either electronically or in paper form in connection with supervision carried out by the rescue authority, such as a fire inspection, and it must be submitted to the wellbeing services county’s rescue authority free of charge upon request (sections 80(2) and (3) of the Rescue Act). It is important that the documents related to the civil defence shelter are stored appropriately and that the storage location is such that they can be found if necessary. Such documents include a civil defence shelter floor plan, the manufacturer’s instructions for use and maintenance, functional capacity inspection records and a plan for activation and use. Documents related to civil defence shelters are often stored in a folder in the vicinity of the civil defence shelter’s ventilation device so that they can be easily accessed during inspections and possible activation. Copies of documents, either in electronic or written format, should also be stored elsewhere, for example in case of vandalism. 26 Publications of the Ministry of the Interior 2026:3 3.4 Updating the plan The rescue plan, including the plan for the activation and use of the civil defence shelter, must be kept up to date (section 2(3) of the government decree on rescue services 407/2011). The up-to-dateness of the plan can be assessed regularly, for example, in connection with updating the rescue plan or the annual maintenance of the civil defence shelter. When updating the plan, assess not only the up-to-dateness of the content but also whether the planned operating models continue to be feasible. The assessment must take into account, among other things, the users of the property and their capability to receive information about a threat and moving to the shelter, as well as potential hazardous situations during protection. If necessary, civil defence shelter maintenance will be carried out on the basis of the assessment, missing preparedness materials will be obtained, and planned operating models and instructions will be updated. 27 Publications of the Ministry of the Interior 2026:3 4 Preparation for the activation of a civil defence shelter 4.1 Basics of activation Info box. Civil defence shelters, equipment and devices shall be kept in such a condition that the civil defence shelters can be activated within 72 hours. Section 76 of the Rescue Act 379/2011 End of info box. Pursuant to section 76 of the Rescue Act, it must be possible to activate a civil defence shelter within 72 hours. This requires that the civil defence shelter is used in normal conditions in such a way that the preparation of the shelter space is possible within this time. Therefore, structures or equipment that cannot be removed within 72 hours may not be installed in a civil defence shelter. Installation or demolition work requiring special expertise, such as electrical and HVAC installations in walls to be demolished during the activation phase or energy storages, may also prevent the activation of a civil defence shelter within the required time. The materials and tools necessary must be reserved for the activation of the civil defence shelter, and it must be technically possible to activate the shelter. For example, the doors, hatches, normal-conditions ventilation and other penetrations of the civil defence shelter must be closed tightly. As a rule, the activation is carried out by the building’s own users, and it may not be certain who is present when the activation order is issued. The aim is that the plan for activation and use will also make it possible to prepare the shelter by persons who have not received previous orientation or training related to civil defence shelters. 28 Publications of the Ministry of the Interior 2026:3 Figure 8.  Communications, material preparedness and activation tasks will be planned in connection with the activation of the civil defence shelter. COMMUNICATION MATERIAL PREPARATION STANDBY ACTIVATION TASKS Providing information Organisation Supplies Construction and equipping Communication devices Civil defence shelter ready for use Commissioning of technical systems Tools Clearing and preparing the space 29 Publications of the Ministry of the Interior 2026:3 The plan for the activation and use of a civil defence shelter must include information on how the activation will be carried out for the shelter in question. In order for the plan to be executed, it must include not only a description of the required work phases but also information on the tools and other aids needed for demolition, construction and operation. It is also recommended to assess the required personnel resources in advance already at the planning stage. 4.2 Organisation As a rule, the activation of a civil defence shelter is carried out by the building’s own users. If this were not possible for some reason, it is recommended to plan and reserve external resources in advance. External assistance or shared use of resources can be planned, for example, with other properties in the immediate vicinity or other actors in the organisation. It should be noted that ensuring the availability of external resources in emergency conditions may be difficult and may involve many uncertainties. In the early stages of activation, it is recommended to use the persons responsible for normal-conditions maintenance of the building, if possible. It is a good practice that some of the users of the property are trained and familiarised with the activation and use of the shelter in advance. It is recommended to train several people, which makes it more likely that at least one of them will be present if the activation of civil defence shelters is ordered. The tasks related to the activation of the civil defence shelter must be planned and described in advance. Among other things, people are needed to steer the activities and carry out various practical tasks, such as emptying the shelter, dismantling structures, and cleaning and equipping the shelter. The plan for activation and use describes the content of the tasks and the competence required by them. The tasks should be described in such a way that a person not familiar with the civil defence shelter can also carry out the tasks in accordance with the plan. The equipment manufacturer’s operating and maintenance instructions can be used in the description of the tasks. People can also be familiarised with publicly available instructional videos on how to activate and use civil defence shelters. It is also possible to attach task-specific instruction videos to the plan and use photographs and floor plans to illustrate written instructions. 30 Publications of the Ministry of the Interior 2026:3 A short bulletin describing, among other things, measures related to the activation of the civil defence shelter should be prepared as an attachment to the plan. In addition, the bulletin should provide guidance on how to move to the shelter, what should be taken to the shelter and how taking shelter takes place in practice. Clear language and images should be used in the bulletin. It is advisable to ensure that the manuals are available in the appropriate languages. For example, translation applications available on the Internet can be used. The bulletin will be distributed to the users of the property at the beginning of the activation. 4.3 Material preparation In order for a civil defence shelter to be activated within 72 hours as required by the Rescue Act, the devices and supplies required for its activation and use must be allocated for the shelter. In addition to section 76 of the Rescue Act, the requirement for material preparedness is also based on section 14(1)(2), pursuant to which the owners and occupants of buildings and business and industrial operators must for their part prepare for the protection of persons, property and the environment in dangerous situations. Civil defence shelters differ from one another in terms of the person capacity, size, location, time of construction and equipping of the shelters, so the needs for material preparedness also vary. The required materials and supplies mainly depend on what is required in the practical implementation of the activation and use plan of the civil defence shelter in question. Materials must be procured in advance, as protective material, tools and accessories will be available to a very limited extent in emergency conditions. Under section 12 of the Rescue Act, civil defence shelter supplies and equipment shall be kept operational and appropriately serviced and inspected. The appropriateness of the supplies can be assessed in connection with the maintenance and functional capacity inspection. When preparing the plan for activating a civil defence shelter, it is advisable to assess the adequacy, usability and condition of the supplies required for the activation and use of the shelter. When replacing devices and supplies of civil defence shelters, their properties and durability must comply with the technical requirements of the regulations in force. 31 Publications of the Ministry of the Interior 2026:3 The materials and supplies of a civil defence shelter are often stored in a locked space in the civil defence shelter. If the equipment and supplies of the civil defence shelter are stored elsewhere than in the civil defence shelter, the plan must describe where the supplies are stored and how it is ensured that the supplies are available when the civil defence shelter is activated. Provisions on some civil defence shelter equipping, such as toilets, reserve water tanks and communications equipment, are laid down in a decree of the Ministry of the Interior on technical requirements for civil defence shelters and the maintenance of civil defence shelter devices (506/2011). The government decree on civil defence shelter devices and supplies (409/2011) contains provisions on other requirements for devices as well as the information and instructions supplied with the devices. 4.4 Activation tasks This section contains a list of tasks typically related to the activation of civil defence shelters. More detailed instructions on how the measures will be carried out in practice must be prepared for each civil defence shelter. The tasks are not in chronological order, as the order in which they are carried out must be planned for each civil defence shelter. Multiple tasks can be performed at the same time. When planning the order in which tasks are carried out, it is important to take into account how many people can work in the shelter at the same time and the time it takes to complete the tasks. For example, filling water tanks with a hose can take ten hours or more. During the activation phase, it is ensured that during the sheltering situation, the civil defence shelter and its equipment work as planned and provide the necessary protection. At the same time, the measures to be taken during the activation will familiarise the coming users of the civil defence shelter with its use. During the activation phase, no faults or deficiencies requiring repairs or maintenance measures should be revealed in a properly maintained civil defence shelter. However, it is possible that something has not been noticed before, or that a fault or omission has only occurred after the previous servicing. With regard to 32 Publications of the Ministry of the Interior 2026:3 maintenance and servicing, the device manufacturers’ manuals must be followed and, if necessary, a professional familiar with the maintenance of civil defence shelters must be contacted. The Ministry of the Interior has published a separate guide on how to maintain and inspect civil defence shelters (2025), which discusses issues related to the maintenance of civil defence shelters in more detail. 4.4.1 Emptying and preparing the space It is advisable to start planning the activation by specifying the location of different functions in the civil defence shelter and the uses of the different areas of the shelter. A plan for activation and use of a civil defence shelter is often accompanied by a civil defence shelter schematic, which typically describes the location of the most important functions, devices and supplies of the civil defence shelter and the structures to be demolished during activation. It may be necessary to make changes to the building’s original civil defence shelter drawing in terms of the layout of the functions. An example of a civil defence shelter drawing showing the uses of the different areas of the shelter is shown in Figure 9. Separate facilities may already have been reserved in large civil defence shelters during the construction phase, for example as a first aid and medical room or a control room. In smaller shelters, it is also possible to plan which spaces are reserved for resting or stay, for example, and which spaces are needed for other shelter functions. It should also be noted that, for example, it is usually impossible to move the water tanks after they have been filled. Sensible placement of the functions may reduce the noise and odour nuisances caused during the use of the civil defence shelter. 33 Publications of the Ministry of the Interior 2026:3 Figure 9.  An example of a civil defence shelter drawing showing the uses of the different areas of the shelter. Overpressure gauge Common area Smoke extraction hatch Air intake Equipment Resting area X m Water containers Water point Airlock tent Dry toilets Waste containers Passive repeater Overpressure valve Overpressure valve Overpressure valve Emergency escape hatch 34 Publications of the Ministry of the Interior 2026:3 The actual activation of a civil defence shelter is started by emptying the civil defence shelter from the goods of normal-conditions use and dismantling structures that are not intended for civil defence use. Such structures include the structures, partitions and shelves of storage facilities as well as lockers and other furniture in changing rooms. The activation plan indicates which structures are to be dismantled and where the dismantled structures and the goods removed from the shelter are to be moved to. The location may be, for example, other storage spaces in the building or the residents’ flats. If necessary, a separate clearing plan may be drawn up, taking into account the storage location of the goods to be moved and the obligations of any tenants of the premises to empty the shelter. After dismantling and emptying, loose dust and other dirt are cleaned out from the civil defence shelter, the surfaces are cleaned and the spaces ventilated. The entrance routes to the civil defence shelter are planned from outside the building to the door of the civil defence shelter. It is recommended to examine the entrances from the perspective of how people who move in different ways, need different kinds of guidance or use assistive devices can access the shelter. For information on assisting the moving to a civil defence shelter, see section 5.2 of the guide. The entrance routes to the civil defence shelter must be marked from outside the building to the door of the civil defence shelter. Reflective or post-illuminating materials can be used to improve the visibility of labels in dark or dim places. According to the Additional Protocol to the Geneva convention (82/1980, 52 and 66 articles), civilian sites must not be subjected to armed activities and civil defence shelters must be identifiable. It is recommended that the markings be visible from the nearest street so that persons moving around the area can easily find the access routes in all situations. Attention should be paid to the visibility of signs outside the building. The access route to the civil defence shelter must be clearly marked inside the building (Figure 10). Signs intended for marking a civil defence shelter may also be attached in normal conditions, but they will be installed in their place at the latest at the time of activation. The plan for activation and use describes where the signs will be added. The figure shows an example of marking a civil defence shelter with an arrow sign. 35 Publications of the Ministry of the Interior 2026:3 Figure 10.  An arrow sign is used to mark the route to a civil defence shelter. Civil defence shelters are marked with a symbol, which is a blue equilateral triangle on an orange background. (Figures: Ministry of the Interior) Arrangements that prevent or hinder the operation of the civil defence shelter door, such as fire or intermediate doors installed for normal-conditions use, structures built in front of the door, structures for facilitating access and the casing of the civil defence shelter door, will be removed. In addition, a tight closing of the door is ensured; if necessary, the door seals are replaced, the necessary loose thresholds are attached, and the latches, hinges and vibration wedges are adjusted. If, during the preparation of the activation plan, it becomes clear that the door to the civil defence shelter is not in place on its hinges but stored elsewhere, it must be ensured that the door is installed in its place in advance. The installation of a heavy door is rarely possible within the 72 hours reserved for activation if done in addition to the commissioning tasks. In most cases, installing the door to the shelter requires special expertise and aids. The locations of the shut-off valves for the heating, water and sewer of the civil defence shelter are recorded in the activation plan and instructions for ensuring their operation are issued. If the civil defence shelter has automatic fire extinguishing equipment, the operation of its shut-off valve must also be ensured. 36 Publications of the Ministry of the Interior 2026:3 Shut-off valves are needed when the civil defence shelter is in closed mode. If necessary, heating is switched off to prevent excessive rise in the temperature in the civil defence shelter. However, the weather conditions and how the shutting down the heating affects the temperature and humidity of the spaces must be taken into account when preparing the spaces. In addition, it must be ensured that any pipes do not freeze. 4.4.2 Construction and outfitting Cleaning and filling of water containers should be scheduled in the plan as early as possible, right after the area planned for the containers has been emptied and cleaned. The water tanks are cleaned before the shelter is taken into use and, if necessary, when the water is replaced during use. It is not recommended to use organic detergents (i.e., conventional hand washing-up detergents) for the cleaning, as they leave organic residue in the container that promotes microbial growth and reduces the preservation of water. The most efficient cleaning of the water tanks is using chlorite and mechanical brushing. When using chlorite, follow the manufacturer’s instructions for use, such as careful handling of chlorite and plentiful rinsing of the containers with cool water. When handling the water containers, pay attention to the cleanliness of the containers, the hose and the brush, and also to hand hygiene. The water tanks are located away from the toilets and filled directly with a hose reserved for the civil defence shelter. Moving large water tanks is not possible after filling. If, according to the manufacturer’s instructions, the water tank can be stored on top of each other to save space, even if it is full, the tanks must also be filled when stacked on each other. If there are cardboard water containers in the shelter, it should be noted that even a small amount of water on the floor or a leaking inner bag can easily wet the cardboard, breaking the containers and spreading the water on the floor. In the early stages of activating the civil defence shelter, the water containers will be filled if possible, after which the emptying and filling of the containers will be scheduled, for example, weekly. This will keep the water storage time short and avoid the use of chemicals. The filling date should be marked on the water tank. 37 Publications of the Ministry of the Interior 2026:3 Water keeps at room temperature for a few days. When stored for several weeks, changes in smell and taste of the water as well as the mucousness of the containers (mainly aesthetic harm) may occur, but they are not likely to cause any actual health harm. If the water does not appear drinkable, drain the water container with a hose to the drain near the water point or by carrying the water out with containers. It is recommended to clean the water container and the hose before refilling the container. If the reserve water storage period is long and no other water is available, water intended for drinking water may be boiled where possible. If water preservatives are used, particular care must be taken in their dosage and the manufacturer’s dosage instructions must not be exceeded. The operator placing the preservatives on the market is responsible for the efficacy and safety of the substance. If the water supply network works and the tap water is potable, a water point located in the civil defence shelter can also be used. In addition, industrially bottled water can be brought to the civil defence shelter, the shelf life of which is often two years unopened. The location of the shelter’s emergency exit route is recorded in the activation plan along with instructions for preparing the emergency exit route. During the planning phase, it is checked that the shelter has the necessary equipment for commissioning the emergency exit route. When commissioning the emergency exit route, the operation of the hatch in the civil defence shelter, the emergency exit route and its lighting will be verified. The exit opening of the emergency exit route may be located either on the exterior wall of the building or underground, depending on the location of the civil defence shelter in the building. If the exit aperture (vertical masonry wall or metal door) is underground, excavate it during commissioning. The premise is that the soil is excavated while ensuring that no waterproofing or subsurface drains are broken. When making excavations, the safety of persons nearby must be ensured by fencing the excavation (Figure 11). In addition, the excavation is protected from rain and rainwater water by means of tarpaulins, drainage and other necessary measures. 38 Publications of the Ministry of the Interior 2026:3 Figure 11.  The exit opening of the emergency exit route is excavated (figure on the left) during activation, after which the excavation is covered with tarpaulins and fenced (figure on the right). (Figures: Ministry of the Interior) If there is a smoke extraction hatch (horizontal metal hatch out) in the emergency exit route, it can be used as an alternative way out in case of danger, instead of the actual exit hatch if the building has not collapsed on the hatch. The smoke extraction hatch is unlocked from the outside during activation. Ensuring the functionality of the air intake of the ventilation device of the civil defence shelter may also require excavation work. In shelters located on the surface of the ground, the air intake often leads directly through the wall to the outdoor air, but in underground shelters, the installation location of the air intake pipe may need to be exposed by excavating under the ground. The air intake pipe is often stored in the civil defence shelter or in an emergency exit, unless the pipe is pre- installed. The plan for activation and use has the installation location of the air intake pipe marked and provides instructions for the installation of the air intake pipe in the planned location. When planning the activation, it is advisable to consider excavating the connection point of the air intake pipe in advance and covering the opening with a well deck (Figure 12). In addition to facilitating the activation of the shelter, it is also easier to check the functional condition of the civil defence shelter under normal conditions when the air intake pipe can be used during the airtightness test. 39 Publications of the Ministry of the Interior 2026:3 Figure 12.  The left illustration shows a well made for the air intake pipe, which can be covered with a deck. The illustration on the right shows the air intake pipe attached during the airtightness test and during operation. (Figures: Martin Mitikka) The toilet closets will be built in the designated places at the relief valves. At the same time, it is ensured that air can be removed from the toilet closets outside the shelter via relief valves. If there are no ready-to-assemble toilet closets in the civil defence shelter, note in the plan how and from which materials the toilet closets providing visual protection are to be built. In civil defence shelters built in accordance with the regulations of 1991 and later, toilet closets must be procured in advance. Toilet closets are fitted with toilet containers with lids and inner bags reserved in advance in the civil defence shelter. A deodoriser is added to the inner bag if one is reserved. In the plan for activation, it is also recommended to plan the purchase of toilet paper and, for example, wet wipes or bringing them to the shelter’s toilet facilities from the building’s other facilities. If the conditions allow the use of a sewer and tap water and the civil defence shelter has a water toilet, the water toilet can be used instead of a toilet bowl. In this case, it must be ensured that the water and drain shut-off valves are open. 40 Publications of the Ministry of the Interior 2026:3 The civil defence shelter is equipped with waste containers with lids and their inner bags. If the waste containers and bags have not been reserved in advance, instructions on how to purchase them or bring them from other premises in the building will be provided in the activation plan. To reduce the odour, it is advisable to instruct that odour-producing and perishable waste be sorted separately from other waste. At the end of the construction and equipping phase, an airlock tent is attached to the shelter door in the designated location or, if there is a separate airlock room in the shelter, the functionality of its doors is verified. The instructions for assembling the airlock tent are included in the airlock tent packaging, in which case they can be referred to directly in the plan for activation and use. It is recommended to ensure the existence of the tools and any other accessories needed for assembly during the planning phase. After installation, the airlock tent is left in the standby or bypass position according to the manufacturer’s instructions. Some of the civil defence shelter space is reserved for resting. Three-tier bunk beds are available for the civil defence shelter, which are durable, take up little space and are quite comfortable in terms of usability. If no ready-made beds have been allocated for the civil defence shelter, it is planned whether, for example, residents will bring their own mattresses and sleeping bags or how sleeping arrangements will otherwise be arranged. However, it should be noted that the only 0.6–0.75 m2 of shelter space is allocated per person. For general use and meals, it is possible to allocate a small table and a few chairs for shared use as well as some necessary equipment, such as a refrigerator, water heater or coffee maker, hot plate or microwave oven. Furniture and electrical equipment must be designed in proportion to the space. However, they must be removed from the shelter if they interfere with the operation there or introduce excessive heat to the shelter. It should also be noted that the electricity supply may be sporadic and interruptions may be long, during which the use of electrical equipment is not possible. It may be necessary to spend long time in shelters or go there repeatedly, so the plan should also take into account how the shelter can be equipped to be comfortable. It is recommended to bring a radio and television to the shelter, which can be used both as a source of information and for entertainment purposes. Drawing and note-taking paper, games, toys, pens and books for shared use can also be reserved. 41 Publications of the Ministry of the Interior 2026:3 4.4.3 Commissioning of technical systems The commissioning of technical systems includes preparing the civil defence shelter’s own ventilation system for use and verifying the operation of other devices and supplies. When drawing up the plan, the instructions for the use and maintenance of the devices in the shelter in question must be taken into account, usually stored in the vicinity of the devices of the civil defence shelter. If the instructions originally supplied with the device or equipment have been lost, the manufacturer of the equipment may provide new ones. The normal-conditions ventilation of the civil defence shelter is closed by removing the ventilation ducts from the penetration pipes and attaching shut-off flanges on the penetration pipes. Before mounting, the condition of the shut-off flanges and their seals, bolts and nuts is checked. Normal-conditions ventilation ducts should be pre-cut and easily detachable and reconnectable. The ventilation ducts must also be removed during a regular airtightness test. The functioning of the civil defence shelter’s own ventilation device and technical solutions related to ventilation, such as overpressure valves and overpressure gauge, is ensured in accordance with the device manufacturers’ operating and maintenance instructions. The manuals are usually stored in the vicinity of the devices on the wall or, for example, in a small tool box attached to the ventilation device. Possible fire breaks or other insulation that prevents the valves from operating will be removed from the relief valves. The condition of the distribution ducts of the civil defence shelter’s own ventilation device, including pipe attachments and valves, is checked and any dirt and debris is removed from the ductwork. The special filter of the ventilation device must be fitted with rubber protective covers which are closed air-tightly and sealed at the time of manufacture. The filter covers must not be opened except in a sheltering situation when starting filtration operation according to the instructions of the authorities. Class B and C shelters built in the 1960s and early 1970s have either a sand filter only or both a sand filter and a large special filter standing on the floor on its own legs. The condition of the sand filter can be visually assessed from the maintenance hatch or the filling aperture. Remove debris and other impurities not part of the filter. Attention should also be paid to the condition of the connection hoses to be attached to the special filter and the sand filter. 42 Publications of the Ministry of the Interior 2026:3 The operation of the ventilation unit’s pressure valve is checked by opening and closing the valve. If there is reason to assume that the pressure valve has been kept open, it is also recommended to check the condition of the pressure valve pre- filter. If the pre-filter is dirty, replace it with a new one. If the ventilation unit is equipped with a preheater, test its operation by switching on the power. If other checks in accordance with the manufacturer’s instructions are required in order to ensure the functioning of the ventilation, these must also be carried out. Once the functional condition of all technical solutions in the shelter’s ventilation system has been verified, the functionality of the devices and the civil defence shelter as a whole will be tested by means of an airtightness test in accordance with the manufacturer’s instructions. If there are emergency power units in or outside the civil defence shelter, their functional condition will be ensured. Communications are tested when the doors and hatches of the shelter are closed. Under section 19 of the Ministry of the Interior decree on the technical requirements for civil defence shelters and maintenance of civil defence shelters, a civil defence shelter must have a technical system or a telephone service point that is already connected to the telephone network either as a separate connection or as a parallel connection to a telephone in the building. Fixed telephone lines are rare today, so the majority of civil defence shelters use mobile communications. The signal of mobile networks typically disappears when the civil defence shelter doors and hatches are closed. If the civil defence shelter does not have a fixed telephone connection connected to the telephone network, the operation of the communication equipment must be ensured by installing a technical system enabling a mobile device, such as a passive repeater, which does not need an external power supply. Also in old civil defence shelters without a functional telephone subscription, the telephone service must be replaced by a technical system in accordance with the Ministry of the Interior decree in force. The installation of a passive repeater or other technical system cannot be left to be carried out until the activation of the civil defence shelter. Instead, the system must be installed in advance. The signal of the mobile network with the civil defence shelter doors closed should be ensured in connection with the preparation of the plan for activation and use. 43 Publications of the Ministry of the Interior 2026:3 The regulations do not require that a network connection (fixed or mobile network) is available in the civil defence shelter, but accessing and communicating information is important in a sheltering situation. If the mobile network is working, communication is usually very limited, and in case of sheltering, it may be necessary to restrict the use of the network. If necessary, instructions are provided to set devices using a network connection to flight mode so that the personnel using the civil defence shelter can connect to the network. Both the communications required in a sheltering situation and the comfort of the civil defence shelter can be improved by installing a Wi-Fi network in the civil defence shelter as well as sufficient fixed outlets for charging mobile devices. When planning the activation, it can also be considered whether it is possible to connect a broadband connection to the shelter in connection with the activation in order to improve communication connections and increase the comfort of the shelter. Access to mobile devices can also reduce the anxiety caused by the situation and maintain people’s mental capacity to cope in a difficult situation. Information on the situation outside the civil defence shelter can also be obtained by radio or television. The working of antenna signals should be tested already in the planning phase. During the activation phase, the devices are connected and tested. Radio reception can also be enabled in the civil defence shelter during power outages by reserving a radio that works with batteries and by placing the device near the passive repeater’s indoor unit. A passive repeater provides reception of the mobile phone and radio only in the proximity of the repeater, usually at a distance of only about one metre. At the end of the activation, the civil defence shelter is left in standby mode. One can move to a standby shelter quickly, and the devices are ready for use for a sheltering situation. The shelter is also left in standby mode between sheltering situations, i.e., whenever there is no need for protection and there are no people in the shelter. As the normal-conditions ventilation of a civil defence shelter has been stopped in connection with the activation measures, adequate ventilation of the shelter in standby mode must be planned separately for each shelter. The shelter’s doors, hatches and relief valves can be kept open if possible, allowing the shelter’s air to be exchanged by gravity. If necessary, ventilation can be boosted by starting the shelter’s ventilation unit in bypass operation. It is important to keep the pressure valve of the ventilation unit closed at all times when the ventilation unit is not in use. This extends the service life of the filter of the pressure valve and prevents the filter from getting contaminated by outdoor dust and other contaminants. 44 Publications of the Ministry of the Interior 2026:3 5 Preparations for protection and the use of the civil defence shelter 5.1 Division of tasks during sheltering During sheltering situations, civil defence shelters and their devices are primarily used by the building’s own users and any other shelterers. Tasks during the sheltering can be distributed at the time of activation or separately in each sheltering situation if the users of the shelter vary from one situation to another. The operating personnel of a civil defence shelter refers to all persons who are currently carrying out a task necessary for the use of a civil defence shelter. Various civil defence shelter tasks are presented in Figure 13. 45 Publications of the Ministry of the Interior 2026:3 Figure 13.  In a sheltering situation, there are various tasks to be performed in a civil defence shelter, related to maintaining the operation of the shelter. In addition, time can be spent in many different ways in a civil defence shelter. Guidance and assistance Door guard Maintaining situational awareness Equipment maintenance Cleaning Operation of ventilation machine Play Reading Remote work Media and �lms Meals Rest Socialising Mental support Caring for children 46 Publications of the Ministry of the Interior 2026:3 It is a good practice to designate a person or persons to manage the use of a civil defence shelter and sheltering situations. The person in charge of the sheltering situation may vary at different times depending on who is in the shelter at the time. If no pre-designated persons are present, the person may be selected from among those present. During sheltering, people are needed, for example, to guide and assist persons moving to and from the shelter, to use the shelter’s ventilation devices, to maintain an overview, and to ensure the tidiness, order, hygiene and waste management of the shelter. If children without guardians are in the shelter, the safety of the children and the necessary support must be ensured during and after sheltering. If the sheltering period is several hours, it is recommended to divide the tasks into shifts. For example, using a ventilation device with a manual crank during power outages is physically demanding, which is why it is recommended to divide the task between several people and into relatively short periods. In a sheltering situation lasting several days, the day can be divided into eight-hour periods, for example, so that each person is in turn either taking care of some of the shelter’s tasks, spending their free time or resting. Depending on the tasks and, for example, the functional capacity of the persons, the work shifts may be of different lengths. In rock shelters and other larger civil defence shelters, there may be a large number of sheltered persons, and there may be a large number of occasional shelter users among those entering the shelter. Guiding a mass of people to shelter and smooth operation during sheltering requires that people are assigned to different special tasks. Compared to small shelters, large civil defence shelters also have different and more demanding technology, the use of which requires special expertise and prior familiarisation. For this reason, persons responsible for the use of large civil defence shelters are often designated, reserved and trained in advance. Special tasks in large civil defence shelters may include directing people to shelter, operating the shelter’s devices, maintaining safety, children’s well-being and teaching, food, water and waste management, and first aid and mental support. It may also be necessary in smaller civil defence shelters to designate persons for these tasks if, for example, there are several smaller civil defence shelters next to each other. 47 Publications of the Ministry of the Interior 2026:3 5.2 Moving to a civil defence shelter The users of the building are informed of the need to move to a civil defence shelter through the authorities’ warning systems, i.e., public alarms (sirens) and emergency warnings (section 2.4) or by observing events themselves. The plan can include, for example, whether there are general population alarms in the area, their audibility and whether the property has a PA system or other internal communication channel that can be used as an additional warning for the users of the property. It is recommended to plan the access to the civil defence shelter in advance. In the planning, it should be noted that in order to ensure rapid sheltering, it is typically not suitable to lock the route to the civil defence shelter between times of use. If necessary, supervision can be arranged at the entrance. In emergency conditions, when civil defence shelters are ready for use, people take shelter in the shelters at the request of the authorities. On the other hand, in emergency conditions, civil defence shelters can be accessed without an official request. Although civil defence shelters are usually designed for the use of persons living, working or otherwise present in a building, shelter can be taken in them by any person in need of shelter in the vicinity if they do not compromise the safety of other persons in the shelter. The entrance routes to the civil defence shelter must be marked from outside the building to the door of the civil defence shelter. Guiding and assisting people in moving to the shelter is planned according to the entrance routes of the site. The aim is to plan the entrance route to be as clear and accessible as possible. People may have various physical and sensory impairments, illnesses or injuries affecting their functional capacity. Children and elderly people may also need different types of support. In practice, this may mean, for example, guiding a person in need of assistance and assisting their walking, carrying them in a staircase, assisting them over a threshold or using any assistive devices, such as a mobile ramp at the shelter door. When sheltering, the doors of the civil defence shelter are closed tightly. However, persons must be admitted to the civil defence shelter for as long as there is room there and this does not pose a danger to other sheltered persons. The civil defence shelter and its use have been designed so that more people can be admitted to it also in the middle of a protection situation. However, if it is suspected that the outdoor air contains dangerous substances, the opening of the enclosure door should be avoided as far as possible. In cases of force majeure, the door must be opened in accordance with the manufacturer’s instructions. If the incoming person has been exposed to radiation or chemical substances, the clothes and accessories 48 Publications of the Ministry of the Interior 2026:3 must be cleaned outside the shelter or in the airlock and cleaning space and, if necessary, the skin must be rinsed with water. The person must wait a while before entering the shelter in an airlock tent or room to allow the contaminated air to exit through the overpressure valves. No contaminated clothing or equipment must be brought into the shelter. In order to allow persons to enter the door, a guard may be posted at the door to ensure the closing and opening of the door in accordance with the manufacturer’s instructions. If necessary, the guard may also otherwise monitor the entrance of the civil defence shelter and, among other things, see to it that the sheltered persons do not bring items prohibited in the civil defence shelter instructions. Especially in larger shelters, it may also be necessary to guide the sheltered within the shelter to provide everyone with reasonable space. 5.3 Modes of use of civil defence shelters The different modes of operation of a civil defence shelter are bypass, closed and filtration. At times when there is no need for sheltering, the shelter is left in standby mode. The plan for activation and use should describe the basic principles of the different modes of use of the civil defence shelter and their use cases. The plan may refer to the manufacturer’s instructions for the ventilation device, which provide instructions on the use of the civil defence shelter in different situations and the transition between different modes of use. These instructions are often stored in the tool box of the ventilation unit. The instructions also describe how to exit or enter the shelter in its different modes of use. Changing from one mode of operation to another can be carried out during sheltering and does not pose a risk to the persons in the shelter. However, compliance with the ventilation device manufacturer’s instructions is important for the operation of the civil defence shelter and the safety of the sheltered persons. The necessary measures are fairly easy and quick. It is recommended to specifically designate persons who will familiarise themselves with the operation of the shelter’s technology and ventilation devices more thoroughly than others, and thus know how to smoothly operate the technology. 49 Publications of the Ministry of the Interior 2026:3 5.3.1 Standby mode Info box. In standby mode, the civil defence shelter has been prepared for use. In standby mode, one can move to the shelter quickly and the devices are ready for use for a protection situation. End of info box. The civil defence shelter is kept in standby mode when it has previously been prepared for use and between different sheltering sessions. In standby mode, the shelter’s doors, hatches and relief valves can be kept open if possible, allowing the shelter’s air to be exchanged by gravity. In standby mode, it is recommended to ensure sufficient air circulation by using the ventilation device of the civil defence shelter regularly with bypass operation. The pressure valve of the ventilation unit must be kept closed at all times when the ventilation unit is not in use. This extends the service life of the filter of the pressure valve and prevents the filter from getting contaminated by outdoor dust and other contaminants. Figure 14.  In standby mode, the civil defence shelter is ready for use. 50 Publications of the Ministry of the Interior 2026:3 Transition from standby mode to either bypass or closed operation is quick. In bypass mode, all doors and hatches are closed and the shelter’s own ventilation equipment is used, which is always ready for use in standby mode. All doors, hatches and valves as well as ventilation are closed when switching to closed operation. 5.3.2 Bypass operation Info box. Bypass operation refers to the most typical use of the ventilation device in a civil defence shelter: outside air passes through the pre- filter directly through the bypass air pipe and through the distribution ducts to the civil defence shelter. Bypass operation is used when there are no toxic gases or radioactive substances outdoors, in which case there is no need to filter incoming air through a special filter. End of info box. If there are no toxic gases, radioactive substances, plenty of dust, smoke or other harmful substances in the open air, sheltering is usually started with bypass operation. Bypass operation is the most common mode of civil defence shelter use in a sheltering situation. In bypass operation, outdoor air is led through the bypass duct and distribution ducts directly to the civil defence shelter at full power, so the air changes rapidly. Bypass operation is used when there are no toxic gases or radioactive substances outdoors, and thus there is no need to filter incoming air through a special filter. If there is a lot of dust, smoke or other contaminants outdoors, the ventilation must be stopped and closed operation must be started. 51 Publications of the Ministry of the Interior 2026:3 Table 1.  Principles of bypass operation in brief measure effect on the operation of the shelter the exterior door and hatches are closed provides protection against pressure and fragment effects the ventilation device is used either with electricity or by rotating the cranks enables ventilation in the shelter pressure valve is fully open air is exchanged in the shelter as efficiently as possible air flow meter’s control lever (if the device is equipped with one) is in bypass position the air flow meter shows the correct reading and enough air is released into the civil defence shelter overpressure valves are freely open air is removed from the shelter via relief valves. If necessary, the relief valves close due to a pressure shock. the water shut-off valve is kept open if necessary water from the water supply network can be used in the shelter if the network is operating the sewer shut-off valve is kept closed and is opened if necessary, for example when using a water toilet or other water points the shut-off valve prevents waste water from entering the civil defence shelter as a result of a possible pressure shock the heat shut-off valve is kept open if necessary the temperature of the shelter is regulated the airlock tent is in the bypass operation mode or the exhaust air valves of the airlock room are fully open to the shelter the civil defence shelter can rapidly shift to filtration operation the special filter or sand filter is not in use outdoor air is breathable without filtering. Special filter covers are closed. 52 Publications of the Ministry of the Interior 2026:3 Figure 15.  In bypass operation, outdoor air is led through the bypass duct and distribution ducts directly to the civil defence shelter at full power, so the air changes rapidly. Detailed, shelter-specific instructions on the use stages and how to change between them are provided in the ventilation unit manufacturer’s manual, which is often stored in the ventilation unit’s toolbox. 5.3.3 Closed operation Info box. Closed operation refers to a protection level in which no air is taken into or removed from the civil defence shelter. The ventilation in the civil defence shelter is stopped and all doors, hatches and valves are closed. Closed operation is used for a short period of time, for a maximum of a few hours, when switching from bypass to filtration operation and, for example, in a very strong fallout situation, or if there is smoke in the vicinity of the air intake of the civil defence shelter. End of info box. 53 Publications of the Ministry of the Interior 2026:3 Closed operation provides the best possible protection for those in the civil defence shelter. If the civil defence shelter hosts its maximum number of people, the maximum duration of closed operation is approximately two hours. After this, filtering or bypassing operation must be started, as the carbon dioxide level and the temperature in the shelter will otherwise be too high. In closed operation, the shelter is hermetically sealed and provides protection against pressure and shrapnel effects, as well as toxic and radioactive substances. Principles of closed operation in brief: y the outside door and hatches are closed y the pressure valve is closed and the ventilation unit is not in use y relief valves are closed y drain, water and heating shut-off valves are closed y the airlock tent is in the filtration and closed operation mode or the airlock room’s exhaust valves are closed toward the shelter space. Figure 16.  Air is not taken into or evacuated from the civil defence shelter in closed operation. Detailed, shelter-specific instructions on the use stages and how to change between them are provided in the ventilation unit manufacturer’s manual, which is often stored in the ventilation unit’s toolbox. If there are toxic substances in the outdoor air and the situation is prolonged, the closed operation must be switched to filtration, after which the door may be opened for entry, if necessary. 54 Publications of the Ministry of the Interior 2026:3 5.3.4 Filtration operation Info box. Filtration use refers to the protection level in which the spec