CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationMedium
During MEP coordination, an HVAC contractor needs to route a supply duct through a 1-hour fire-rated corridor wall in a multi-family building. What additional component must typically be installed at the penetration to maintain the wall's fire-resistance rating?
- AA fire damper rated for the wall assembly
- BAn additional layer of insulation wrap only
- CA flexible duct connector
- DA vapor barrier around the duct
Show answer & explanationAnswer & explanation
Correct answer: A. A fire damper rated for the wall assembly
When ductwork penetrates a fire-rated wall or floor/ceiling assembly, a listed fire damper (or combination fire/smoke damper where required) must be installed at the penetration to preserve the fire-resistance rating of the assembly. Insulation wrap or vapor barriers alone do not restore fire rating.
Why the other options are wrong
- B. Insulation wrap alone does not provide the required fire-rated closure at the penetration.
- C. A flexible connector addresses vibration/noise, not fire rating.
- D. A vapor barrier controls moisture, not fire spread, and does not satisfy fire-rating requirements.
Fire Damper at Rated Penetrations
Ducts passing through fire-rated wall or floor/ceiling assemblies require a listed fire damper to maintain the assembly's fire-resistance rating.
- Fire dampers close automatically when triggered by heat (typically via fusible link).
- Required at duct penetrations of fire-rated walls/floors per mechanical code.
- Combination fire/smoke dampers may be needed in smoke-rated assemblies.
Memory trick: 'Duct through a rated wall? Damper stops the fire's crawl.'