Specifications include, but are not limited to: The HVAC system includes any interior surface of the facility’s air distribution system for conditioned spaces and/or occupied zones. This includes the entire heating, airconditioning and ventilation system from the points where the air enters the system to the points where the air is discharged from the system. The return grilles, return air ducts to the air handling unit (AHU), the interior surfaces of the AHU, mixing box, coil compartments, condensate drain pans, humidifiers and dehumidifiers, supply air ducts, fans, fan housing, fan blades, air wash systems, spray eliminators, turning vanes, filters, filter housings, reheat coils, and supply diffusers are all considered part of the HVAC system. The HVAC system may also include other components such as dedicated exhaust and ventilation components and make-up air systems.