|Secure Buildings: Indoor Release|
Advice for Safeguarding Buildings
Against Chemical or Biological Attack
Distinguishing between a biological release and a chemical release:
For any indoor release, whether chemical or biological: if evacuation can be done safely, evacuate the building to a meeting point upwind of the building.
Biological release (or unknown):
If possible, stairwells should be pressurized with 100% outdoor air to provide an evacuation route. Other HVAC, and bathroom and utility room fans, should be shut off.
Segregate people known to be exposed, to avoid contaminating others via contact with clothes or skin, and tag or mark these people for medical treatment and decontamination.
For a biological release, the goal is to minimize the total number of people exposed, even if this leads to higher or longer exposure for some people.
Also, for most buildings the normal operation of the HVAC will tend to isolate areas that are served by different air handling units, thus helping to slow the spread of contamination. The isolation is reduced if the HVAC system is not properly balanced, or if the building's air recirculation system mixes air from different supply zones.
If the building operator has checked system operation and is sure that dampers and fans are working correctly, some HVAC manipulations can be beneficial. The simplest such action is to put the building on 100% outside air (no recirculation), with supply and exhaust fans on full power.
If more sophisticated actions are possible, then do the following:
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Airflow and Polutant Transport Group : Indoor Environment Department : Berkeley Lab