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Venting a boiler in a naturally ventilated garage.


Registered User
Feb 3, 2020
Hi guys, how are you!

We are designing for a hotel with its first floor as an open parking.
I was just wondering if I can vent a boiler to the parking garage that is considered open, considering there is enough area at the sides for ventilation.
The mechanical room's wall, where the boiler is located, is around 15' from the edge of the building. Boiler has a category iv vent


Nov 28, 2009
Poconos/eastern PA
801.4 Positive flow. Venting systems shall be designed and
constructed so as to develop a positive flow adequate to convey
all combustion products to the outside atmosphere

Does the manufacturers instructions say you can terminate the vent inside a building?


Silver Member
Jan 28, 2010
Sioux Falls, SD
IFGC 503.3 Design and construction. Venting systems shall be designed and constructed so as to convey all flue and vent gases to the outdoors.

Also, the manufacturer will probably have some requirements/restrictions on termination location with regard to overhangs/corners that if not followed can play havoc with the pressure safety switches in the boiler. Additionally, the steam that will come out of the exhaust is very acidic and will be hard on the structure above, possibly causing it to deteriorate quicker than normal. Depending on the climate, you may have ice buildup issues as well.

You may have the option of coming out of the mechanical room where you want to and then run the vent over the 15' to the exterior as long as you maintain required slope and aren't over manufacturer's length restrictions. Check the manufacturer's restrictions on running vents through unconditioned spaces. Hopefully that route doesn't put it over a public walkway??