Garage Exhaust

[NorPwr]

Situation: Single exhaust fan cannot get another. Two areas to vent, a small garage/workshop and a chemical storage area. The National Building Code states that garage has to have dedicated exhaust. I want to install a damper system that makes the fan vent the garage during the day when it is in use and vent the chemical room during the night when it is a problem. Is this permitted?

 

[HVAC68]

Does your chemical storage room warrant an explosion proof fan ? Check this out, since some of them do require.

HVAC68

 

[NorPwr]

No there are no special requirements for the chemical storage area. The garage would only be in use from 8-4pm daily and the chemicals only emitt fumes from 6pm-6am daily. So I was thinking that if the code allowed it I could install a damper system that would switch the two rooms accordingly.

Regards,

 

[CountOlaf]

If your situation that you've described is indeed corect, it theoretically sounds OK to me. I would check the code to see if there's a definition section which elaborates on the term "dedicated". At any rate, it sounds "uniquely legitimate." If you're getting permits pulled, etc., you have a legitimate argument and may want the AHJ's approval for your alternative interpretation or the requirements.

You'll of course have to check that the fan is capable of providing the minimum amount of exhaust required at the most demanding space. If it's a constant speed fan, the area that's farther away will have a presumably larger static pressure drop in it's duct system, so the airflow for the "closer" space may be greater than that of the "farther space, unless you compensate with volume dampers or duct sizing methods.

 

[Drazen]

Well, I am not specialist for US standards, but some principles apply to almost all world standards related to safety.

I beleive that term "dedicated" really means separate.

Both systems, garge vent and chemical storage have it's own safety concerns which are not compactible. In addition, how do you plan to vent chemicals when garage is in use?

For me, it is clear situation: use separate systemss. I know it costs more, but safety is not place to put your saving efforts on.