The ductwork and return air are usually the first items cleaned and checked at most smoke or fire losses. In most cases, this system was operating when the fire occurred and it can work to circulate the smoke odor throughout the building. The interior of this duct system is often galvanized metal and an excellent surface to attract soot which must be either removed or immobilized before the system can be used. We purge these of all the soot that can be physically removed and a sealant is then fogged into the ductwork system to ensure there is no fallout. The Heating, Ventilation and Air Conditioning (HVAC) unit will then be inspected to determine the extent of soot in the unit. The filters in all these HVAC units will either be cleaned or removed to remove any odor and residual soot.