HVAC Systems: Affected by a Fire
HVAC systems condition the air within occupied interior spaces. They ventilate and supply warm or cool air through an air conveyance systems referred to as ductwork. HVAC systems typically have a cold side, or return air, and a hot side, the supply air. An air filter system is normally strategically located on the return side, somewhere before the blower motor compartment. Most air filters are engineered to capture smaller airborne contaminants in order to protect the blower compartment components.
Although HVAC systems all have the same purpose, they vary greatly in design. Soot and smoke odor removal is relatively easy in some types, especially metal ducts. However, following a structural fire, soot contaminates coat most interior fiberglass surfaces. Fiberglass duct insulation is easily contaminated due to the volume of air spaces within the insulation matting. When ducting becomes exposed to smoke odor gases and particulates, PICs penetrate deep within the fiberglass fibers used to insulate the ducting. An HVAC system that was operating during a fire will certainly be more heavily contaminated than one that was turned off; however, systems become contaminated even when they were not operating during the fire.
An inspection of the HVAC system will determine when the complete system requires cleaning. In heavy soot contamination situations, restorable mechanical components within the HVAC system should be disassembled, cleaned and deodorized in accordance with published NADCA standards. NADCA stand for National Air Duct Cleaners Association.