CSLB C-20 HVAC ContractorPlanning and LayoutEasy
On a mechanical blueprint, a duct symbol shown penetrating a rated wall assembly includes a hatched rectangular symbol labeled 'FD'. What does this symbol indicate to the installing technician?
- AA required fresh air damper for outdoor air intake
- BA required flexible duct connector at the wall penetration
- CA required fire damper at the rated wall or floor penetration
- DA required filter drier installed in the duct run
Show answer & explanationAnswer & explanation
Correct answer: C. A required fire damper at the rated wall or floor penetration
The abbreviation 'FD' on mechanical blueprints, especially at rated wall or floor assemblies, denotes a fire damper, which must be installed to maintain the fire-resistance rating of the penetrated assembly per the Mechanical Code.
Why the other options are wrong
- A. Fresh air dampers are typically labeled 'OAD' or similar, not 'FD'.
- B. Flexible duct connectors are typically labeled differently and are not fire-rated devices.
- D. Filter driers are refrigeration line components, not duct penetration devices.
Fire Damper Blueprint Symbol
'FD' on mechanical drawings marks the required location of a fire damper where ductwork penetrates a fire-rated wall, floor, or ceiling assembly.
- Fire dampers maintain fire-resistance rating of the assembly
- Required by Mechanical Code at rated penetrations
- Must be accessible for inspection and testing after installation
Memory trick: FD stops fire from spreading through the duct.