What is causing a bad smell from my house a/c vents?

When the a/c or heater is on it smells up my house. When its off it doesn't smell.

What is causing a bad smell from my house a/c vents?
You might want to check to see if something has died in the unit....... Yukkkkkk
Reply:the furnace filter could be filthy, the ducts could be musty, any number of things. It is normal when you turn the heat on for the first time to get a funny smell, but it should go away soon after the 1st use.





I'd check the filter for starters. Tye are cheap and should be changed monthly, but most people neglect this
Reply:It would help if you could have described what the smell is like.





Mildew/Mold smell? Mildew or mold in the duct work.





Dust smell? Obvious, dust in the duct work.





Rotten decaying smell? A dead rodent in the duct work.





You really need to get someone out to clean your units and the ductwork. Any one of these things listed above can spread disease/bacteria through out your house. Don't take a chance on you or your family getting ill.
Reply:if you can I would pull of a vent and look with a flash light, if really dirty there are companies out there that clean the duct work,
Reply:Could be one of two things .1 a dead animal that may have creeped in there . 2some food that may have fallen into it and is now rotting or molding up in there.Check it out and maybe just by using a mirror and a flashlight you can see the problem.
Reply:Jimmy Hoffer may have been buried there?
Reply:sometimes, Birds will crawl in to your furnace through the vent pipe that is in your chiminy. If it gets in, and can't get out... it might stink.
Reply:well I'd say you need to find out very fast, because if it is some mold , that is a very big health hazard. and mildew can spread through the house. and if it is a animal, well you'll know what to do about that. and if you are very lazy then might i suggest a good cloths pin. lol sorry had to do it.
Reply:you may have a small creature that has died or is stuck? I had something like this at my old home. May want to get someone to take a look.
Reply:Mold or mildew in condensate pan.
Reply:you might have poop in your vents....not entirely uncomman despite how absurd it may sound.