Smell in vent when Heater is running

In a new furnace it takes awhile to break in and you will get a burn-off odor. On an older already broken in furnace it could be a dead mouse.

What sort of a smell? If it's a sort of burning dust smell, it's probably just a bit of dust in the furnace that has collected since its last use and is burning off--nothing to worry about unless you have a tremendous amount of dust there (which would seem very difficult to accomplish without trying).

Depends what kind of smell...

If a musty dusty smell, that's normal due to typical dust that settles in there when not in use. It will burn off in short order and clear up.

But if it's something rank and rude smelling, then possibly a dead rodent in there somewhere.

Smells easily originate at the furnace itself. When it gets hot, accumulated road dust and such burns off.

If it’s a dead creature you would probably smell it all the time. Had “something” die in the wall of our house and it smelled for a very long time. I suspect dust burning off. We’ve had our mh 5 years now but use the heat pump 90+% of the time we need heat. When the furnace kicks in, I get the furnace smell.

mice pee? not ran for awhile could just dirt.turn it on let run for hours .

Our old Ford Four Winds always had a crayon smell when running the heat/defrost in the cab. I searched w/o disassembling the cab but never found the cause. Perhaps some child tossed their crayons on the dash, then they rolled down the defrost vents. Or the kids shoved the crayon(s) into the dash vents.. Who knows.

The house furnace always had a distinct smell, but it was more like warm metal - nothing serious, but was that "ah, the comforting smell of cutting the chill!" sensation.

Our Sunseeker's heat/defrost is clean, where the furnace has always had more of a warm paint smell. After 5 years, it still smells that way while it's running, it never changes. Again, nothing serious, though it still imparts that "ah, the comforting smell of cutting the chill!" sensation.

(Speaking of which, I think my wife is making lunch! It's starting to have that flavorful smell wafting through the home office!!!!)

Yup op. Gotta say what it smells like....

If it smells like butter, I can help you there.... :B
(Some of you will get that one!)

Edit: nvm