Secure Buildings: Pre-Event Advice – Long-Term: Safe Zones
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Last Updated
April 27, 2005

Pre-Event Advice – Long-Term

Establish internal "safe zones" for sheltering-in-place, and exterior locations for evacuation.

For an outdoor release, people should remain indoors.
"Shelter-in-place" rooms can be created or identified, where people can stay in the event of an outdoor release. The goal is to create areas where outdoor air infiltration is very low. Usually such rooms will be in the inner part of the building (no windows to the outside). They should have doors that are fairly effective at preventing airflow from the hallways (e.g. they should have no gap or only a very small gap at the bottom of the door). Bathrooms are usually a bad choice, because they often have an exhaust duct that leads directly to the outside. If the exhaust fan is left on then air will be drawn into the bathroom from other parts of the building, which will become contaminated. If the exhaust fan is turned off, then the duct can allow outside air to directly enter the bathroom. Exhaust fans for bathrooms and utility rooms are often controlled separately from the HVAC system.

Opening and closing a conventional door can pump large amounts of air into the room; replacing the door with a sliding door, if practical, can reduce this effect.

Additionally, it may be possible to provide purified air to the safe area, depending on whether the pollutant can be removed by the building's air filtration system. Modifications to the HVAC system can add filters and an air supply that are dedicated to the safe area.

For an indoor release, people should exit the building.
The chem/bio agent will be carried out of the building through windows, doors, and vents, so people should congregate upwind of the building.

At least two different evacuation zones should be identified in advance, and the appropriate one should be used depending on the wind direction.

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