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Air ventilation in civil defense shelters

Writer's picture: Mikael DenutMikael Denut
Civil Defense Shelter Ventilation Unit

Imagine this: a civil defense shelter where the air doesn’t circulate properly. Sounds absurd, right? Yet, too many overlook the importance of ventilation and equipment—and that could be a mistake that costs lives. This isn’t some hypothetical fluff; it’s reality. When a crisis hits, a shelter isn’t a nice-to-have—it’s the only rule of the game. And if ventilation fails, the game is over.


Here’s the raw truth: the ventilation in a civil defense shelter must filter out external pollutants, toxic gases, and other dangerous substances while maintaining positive pressure to keep outside air from seeping in through even the smallest gaps. This means the shelter’s ventilation systems must be top-notch—and they need to work every single time they’re called upon. In this guide, we dig deep into the core requirements and regulations for civil defense shelters from a ventilation perspective.



General requirements for shelter equipment


The equipment in a civil defense shelter must meet strict requirements—it’s not just about the equipment “working,” but about its performance under any condition:


  • Shock resistance: Equipment must withstand shock loads with a maximum displacement of 1.5 m/s and acceleration of 300 m/s². This means the gear must endure extreme impacts and vibrations without failure.

  • Long service life: The components of the ventilation system must last at least 30 years, while parts attached to concrete structures should endure up to 50 years.

  • Withstand temperature fluctuations: Equipment must remain operational in temperatures ranging from -30°C to +70°C and function properly between -20°C and +40°C. In other words, the system must be ready for anything.


Air ventilation and valves in civil defense shelters

In a civil defense shelter, ventilation isn’t just a comfort issue—it’s a matter of life and death.

Ventilation Ducts in Civil Defense Shelters

  • Ventilation equipment: A shelter must have the right ventilation equipment, such as pressure valves, overpressure valves, and exhaust valves that can handle pressure waves and overpressure. The shelter doesn’t function without them.

  • Overpressure valves: In an S1-class shelter, the overpressure valve must be capable of closing in response to external pressure surges and regulating overpressure impulses. This ensures that the shelter maintains positive pressure, keeping hazardous substances out.



Pressure- and gas-tight structures

Controlling air pressure is everything. If this fails, the entire shelter fails.


  • Doors and Hatches: Shelter doors, hatches, and sealing devices must be both pressure- and gas-tight. They are designed to withstand pressure surges and keep gas leaks out.

  • Seals: The seals on pressure- and gas-tight equipment must be made from durable materials like chloroprene rubber to ensure they withstand time and use.


Gas detection systems and emergency lighting

A shelter’s system must be self-sufficient and operational even when the rest of the world is not.

  • Gas detection systems: These systems detect various hazardous chemicals and warfare gases and provide alarms, even during power outages.

  • Emergency lighting: The shelter must have an emergency lighting system designed to operate for at least 5 hours in a crisis. This provides critical time to react and take action.


Airlock tents and shelter ventilation

  • Airlock tent: The shelter must include an airlock tent that prevents contaminated air from entering and maintains proper internal air pressure.


Negative vs. positive pressure in shelters: Why positive pressure is essential


The importance of positive pressure

A civil defense shelter must always maintain positive pressure relative to the outside air. This means the internal air pressure is consistently higher than the external air pressure because positive pressure prevents dangerous gases, pollutants, and contaminants from entering the shelter. The pressure differential ensures that air flows outward through any gaps or sealing valves, preventing contaminated air from flowing inside.



Avoiding negative pressure

Under normal conditions, a slight negative pressure is often aimed for. However, in a shelter, negative pressure can be catastrophic because it could draw contaminated air inside. The ventilation system in a civil defense shelter is designed to prevent the formation of negative pressure and maintain positive pressure, which is critical for the shelter’s safety.


At IVAeris Oy, we take care of your ventilation

At IVAeris Oy, we’ve seen it all when it comes to ventilation—and we know exactly what it takes to ensure your civil defense shelter’s ventilation works flawlessly. We don’t get involved in equipping or maintaining shelters; for that, we recommend Temet Oy and Presto Oy, who have proven themselves to be leaders in the field. But when it comes to ventilation, we are the real experts who ensure that your shelter breathes correctly and safely.


Ventilation Ducts and Overpressure Valves in Civil Defense Shelters

Below are answers to the most common questions about shelter ventilation. Here, you’ll find more information on how to ensure the optimal functionality of your shelter.


What’s the role of air ventilation in a civil defense shelter?

First things first: Ventilation’s job is to protect. Plain and simple. It keeps the air clean and safe and ensures that nothing from the outside gets in. That means toxic gases, chemicals, dust—anything. Ventilation keeps the air moving and breathable. Period.

Why is positive / overpressure the key to a shelter’s success?

What are the key requirements for ventilation equipment?

What components do you need to know and understand?

How do you ensure ventilation equipment works when needed?

What if the power fails in your shelter?

What if you don’t take care of your shelter’s ventilation?

What’s the formula for success in shelter ventilation?



Get in touch with us today to ensure your shelter’s ventilation is up to standard in all conditions. When others take care of their part, we focus on what we know best—ventilation.


 

WE KNOW, WE CARE & WE GET IT DONE


IVAeris Oy

010 206 3000

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