F80 Smoke Control and HVAC Systems 2

Question 1

Under NFPA 90A, an air-handling system with a capacity greater than what airflow requires a smoke detector in the supply air duct?

Accepted Answer

2,000 cfm

Answer

NFPA 90A requires supply-side duct smoke detection on air distribution systems over 2,000 cfm.

Question 2

Where is the supply-side duct smoke detector normally located?

Accepted Answer

Downstream of the air filters and ahead of any branch connections

Answer

Placing it after the filters and before branches lets it sample all supply air without filter clogging.

Question 3

What is the primary function of a duct smoke detector?

Accepted Answer

To stop the spread of smoke through the HVAC system

Answer

Duct detectors are meant to shut down or control HVAC to prevent smoke distribution, not to serve as open-area protection.

Question 4

A duct smoke detector is installed above a hard ceiling where it cannot be seen. What is typically required?

Accepted Answer

A remote alarm indicator or remote test station

Answer

Concealed duct detectors need a remote indicator so their activation can be seen and identified.

Question 5

Return air systems over what capacity require smoke detectors at each story before connection to a common return?

Accepted Answer

15,000 cfm

Answer

NFPA 90A requires return-side detection at each story for systems over 15,000 cfm serving more than one story.

F80 Practice Test