FEMA 453 Design Guidance for Shelters and Safe Rooms

Relief Damper. In supplying filtered air from the top of the stairwell,
the carbon dioxide concentration in the occupied stairwell
increases with the vertical distance from the source of fresh air,
because leakage paths are evenly distributed along the vertical
axis. To ensure carbon dioxide levels remain within safe limits at
the lowest levels of the stairwell and to facilitate removal of heat
and humidity generated by the occupants, a relief damper was
installed at the lowest level to maximize the flow-path length for
clean air. The relief damper was adjusted to prevent the internal
pressure from exceeding 0.30 iwg, a pressure above which the
doors that open into the stairwell could require more than 30
pounds of force at the door handle to open (depending upon
door closer force).
Door Seals. Weather-type seals were installed on doors into the
stairwell to minimize air leakage around the closed doors. According
to blower door test results, leakage around the stairwell
doors before the addition of weather-stripping and wipe seals was
substantial (approximately 3,000 cfm at 0.3 iwg).
Warning System. A public address system was installed in the
building so that voice messages could be broadcast throughout
the building to notify people at any location of an emergency.
Accessibility. The stairwell offers a point of entry accessible to
wheelchairs, and each landing provides an area adequate for two
wheelchairs without blocking access to the door.
Drinking Water. The stairwell has no accommodation for drinking
water. There were plans to make water available by storing bottled
water in a compartment on each landing of the stairwell.
Communications. Each level of the stairwell has an emergency
telephone and an intercom to provide contact with the security
operations center.
Cost. Total cost of the installed system was $190,000, or about $300
per person sheltered. This does not include the cost of the public
3- CBR ThReaT pRoTeCTion