Central Air is emitting a foul odor like wet or mildew laundry?

Question

I have had this smell for a year or so when he air is on. I have had the vents cleaned, the drip pan & unit checked for mold and I still can smell it. I thought I had a leak in the roof or the siding that is wet causing mildew or mold but had that checkout and no problem. I know the smell is coming from the air but I can't get any one to find the problem. When the air is off for a few days the smell goes away. I have flexible tubes throughout the house and now I am wondering if condensation is causing it. Any suggestions would be appreciated.

Answer 1

I would first make certain the primary drain is equiped with a "P" trap. If the drain does not have a P trap installed it could be allowing unpleaseant odors into your HVAC system as the unit drains into the sewage line. (If it is installed according to code.) If you have so much moisture in your duct to create mold , you should notice rust on the registers in the ceiling or floor). If it were me the first ting I would check is the P trap.  

Answer 2

You have mold in the duct work. The problem with Flex tubes for distribution is that condensation collects in the pleats of the tubes and they never really dry out, a wonderful place for mold to grow is the result. I'm not sure how you really fix this short of replacement of the duct-work/tubing with insulted rigid duct-work. this needs to be fixed though as you will be made sick by exposure to this and the spores will find other places to take up residence in your home.

Astrobuf

Answer 3

You had the primary causes already checked.Sometimes the plenum might have an enduring foul odor.It can be rebuilt and replaced for a couple hundred dollars and would be well worth it if that was the cause.You can cut a 3 inch by 3 inch hole in it and with a flashlight,peer inside it to inspect it.Then just put the piece back and tape it.I wonder if they also checked your squirrel cage and wheel.

Look at those potential causes.

Good luck.

I have demoed ductwork in hundreds of homes and have never found any growth or other undesirables within the fiberglasss flex.It is always in the ductboard.There is a plastic lining on the inside of the flex and it's always pristine even 15 or more years old.That's why I will always believe "duct cleaning" is a scam.