Shutdown

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ryant35

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Location
Cypress, CA
What do they mean by direct exhaust? As opposed to what?

The code this is pulled from talks about supply air over 2,000 cfm. I would imagine direct exhaust would be exhaust fans that do not have any smoke/fire dampers in their ducts.

In my experience, the only time we shutdown exhaust fans, other than smoke control, is if they feed through smoke/fire dampers. Stop the fan to avoid damage to the duct while the damper is closed.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
The code this is pulled from talks about supply air over 2,000 cfm. I would imagine direct exhaust would be exhaust fans that do not have any smoke/fire dampers in their ducts.

In my experience, the only time we shutdown exhaust fans, other than smoke control, is if they feed through smoke/fire dampers. Stop the fan to avoid damage to the duct while the damper is closed.

This is not coming from a standard or code, but appears to be part of a specification or drawing note. A typical case where you might not want to shutdown an exhaust fan would be a Class 1 kitchen exhaust hood.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
IMHO direct exhaust fans exhaust directly to the outside either through ceiling or wall or possibly(?) through individual ducts that do not come together in a common plenum at any point.
The distinction is that even if such fans pull in smoke or flame they do not aid in the spread of same to other parts of the building. Therefore they do not need to be shut down even if they are intaking smoke and therefore they do not need smoke detectors for a stop mechanism nor automatic stopping on alarm.
 
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