Gas Furnace Blows Attic Smell into House


Old 11-23-17, 08:21 PM
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Question Gas Furnace Blows Attic Smell into House


I have a problem with my gas furnace in the attic. When it turn on, I can smell the attic air coming to the vents for about two minutes. I am not able to find the leak, which I think it has. Does anyone have an idea what this might can be?

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Old 11-23-17, 08:44 PM
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Do you have a filter up there that might need to be changed? Some units have multiple filters... some people don't know about the hard to reach ones. And what exactly is attic smell?

I wonder if you might be smelling a burnt dust smell from a dirty, dusty heat exchanger.
Old 11-23-17, 09:18 PM
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What does an attic smell like ?

Normally a smell introduced into the air stream comes in on the return side. Make sure all connections are taped with metal foil tape. It can be impossible to see the bottom of the ductwork.
Old 11-23-17, 09:23 PM
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Test for a leak.

Run the furnace fan and check the temperature of the air going into the return air grills and in the return air duct just before the furnace.

A very significant difference indicates a large return leak.

it's normal to lose a bit of heat though if it's going through an attic duct.

But if it's pulling 68f in and by the time the air reaches the furnace, it's like 58, you know there's something going on.

There are other tests you can do.

when there's no wind, Open a main floor window in a room open to the rest of the house, 100% block the supply vent in that room (u don't want internal pressurization), turn on the furnace fan, go outside and see if there's a lot of indoor air coming out the window. See if there's a big difference with the fan on vs off.

A return leak in the attic will pressurize the house.
Old 11-23-17, 09:47 PM
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It smells like the old fiber insulation in the attic. So, I assume that somehow, the smell gets sucked into the system, but disappears after 2 minutes of airflow.

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