We installed (NY) a new gas heater/central air unit last Fall. Heat was fine all NY winter but when we ran the central air for the first time (5th now) it fills the entire 1200 sqare foot house (one floor home with basement) with a gas like odor. When I walk in after its on for a few hours, I immediately have to shut down and open every door and window in the house. Spouse can't barely smell (males do not have same smell sense but his must be dead) it but 2 friends could immediately smell when they opened the door. House is 30 years old and dehumidifier runs often. Installer came by and trap was put into the condensate drain. Husband taped in filter, filter is clean. Husband built house and knows house construction. House is not on sewer, we have a septic. I have read over 50 similar posts on the internet and have showed all to spouse hoping to find an answer. In other words, we have not found the answer through any posts when searching for gas smell central air and similar searches. Please help... it's hot now and July is tomorrow and it's hot and humid in western NY.

Did you just start using your dehumidifier? Gas smell as in sewer gas, route egg smell, gasoline solvent smell, dead mouse smell, moldy smell?

I've seen the problem many times on a Google search. For others, this is what I found out after a lengthy conversation today with an HVAC person when inquiring about a through duct cleaning (this may or may not help you). The person was not trying to sell me the duct cleaning as it was a new unit and we never had central air before so he didn't feel it was in the ducts or a problem with the AC unit. He advised me to let the AC unit run as it works like a dehumidifier and that the smell was probably the wet basement air circulating into the ducts. We ran the dehumidifier today that picked up a quart of water in a very short time span. He was right on... it was the musty smell from the basement circulating through the ducts and running the AC all day as he suggested vs open the door and windows after about 2 hours when the smell was overpowering. We also cleaned some of the basement walls at the base and threw out a few rug pieces that we would wipe our feet on as the rug pieces held the stink of the musty basement... I think we're on the other side of the problem now and enjoyed the cool air today in the 90 degree heat...

I am glad you found the problem. Thanks for letting us know! Our only pay is when someone responds with a positive result.