I know burning gas need oxygen -- means fresh air. However, I checked my furnace and heater I didn't see any fresh air supply around.... They seems just get fresh air from the garage.

I am asking the question because I am going to seal my garage door...

My home was built at 2003. It shouldn't be too old....

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    You do need air if the garage is tightly sealed with no fresh air supply you will have problems and may create the possibility of carbon monoxide buildup if there is not enough draft for the nasties to vent.
    – Ed Beal
    Commented Oct 30, 2016 at 14:19

1 Answer 1


A "make-up air intake" or "combustion air intake" can provide a path for combustion air when a furnace wasn't designed for a direct external conduit:

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