Outdoor Releases

Once the formation of a toxic cloud has been confirmed there are only two courses of action available to the occupants of buildings: evacuation, which implies enough time and opportunity to exit the building and outrun the toxic cloud, or sheltering-in-place (i.e. remaining in a Toxic Free Area (TFA) within the building).

The toxic cloud will drift at a rate determined by its composition, wind velocity and other climactic variables. It will travel over and around buildings and other obstacles following a course of least resistance. A building, which is essentially a system of barriers comprised of exterior and interior walls, doors and windows, will provide some passive protection from airborne hazards. The degree of protection is directly related to the nature and concentration of the toxins within the cloud, duration of exposure and integrity of the sealing of the structure. Building air intakes attached to the HVAC system pose a significant risk in that they can quickly draw the contents of a toxic cloud to the inside of the structure. If the building is not equipped with an integrated collective protection filtration system such as the Hunter FFA series filters, these systems must be shut down and sealed as soon as possible after an incident occurs. All windows, doors and other known air inlets should also be immediately shut and sealed.

If the building is equipped with an integrated collective protection filtration system, the occupants must move immediately to the designated Toxic Free Area (TFA) where they can remain safely until the threat has passed.

A successful shelter-in-place strategy requires a well-sealed room with a reliable air filtration system in place. Effective collection protection filtration systems operate based on the principal of positive pressure or over pressurization where the air pressure inside the TFA is greater than the pressure outside. This pushes the clean or filtered air from the TFA out through any tiny cracks or non-sealed areas around the TFA and prevents contaminated outside air from entering through those same openings. This over pressurization provides clean, breathable air at a rate which will support a predetermined number of individuals over an indefinite period of time based on the facilities, food and water.