Fire Protection Considerations for HVAC
HVAC work must not undermine fire separations or opening protection. A fire separation is a construction that resists the spread of fire; in houses, common examples include the separation between an attached garage and the dwelling, and separations between dwelling units. Ducts, vents, and pipes that penetrate a required fire separation need protection so the assembly's integrity is maintained. That protection may be a fire damper, a fire-rated duct assembly, or a listed firestop system, depending on the assembly and the Code exception. Fire dampers must be installed in the correct orientation, with access for inspection and testing.
Opening protection includes fire-rated doors and closures; HVAC openings must not create an unprotected path. A furnace room that is a required fire separation needs appropriately protected openings. Combustion-air openings and duct penetrations must be firestopped with listed materials, not stuffed with paper or unfaced insulation.
Traps: assuming every duct penetration needs a fire damper (some residential exceptions exist), and assuming no damper is needed because the building is a house. Another trap is to penetrate a garage separation with a supply duct or door grille and not restore the separation.
Worked example: a basement furnace duct rises through a floor assembly that is a required fire separation between dwelling units. The penetration must be protected by an approved method; a generic plastic sleeve or unprotected galvanized duct is not acceptable. Check the specific Code exception before selecting a damper, and have the assembly inspected before concealment.