If you are smelling a bad odor in your home and cannot seem to find where it is, you should check your air conditioner. Some problems with HVAC units can put a bad odor in your home through the duct system.
If your home smells like a sewer, you could have a dead animal in your duct work. Animals may look for a cool place to get to when it gets hot outside, and one of these places may be in the crawl space of your home. Once their bodies start to decompose, there will be a sewage smell. It could also be due to something much worse, which is methane gas. There could be a leak in the duct work, or there may be a ruptured sewer vent pipe or line located near the air duct system. This can be dangerous so call a plumber to inspect your plumbing. If they do not find anything wrong, it is likely your HVAC system.
Dead Animal Smell
If you are smelling a horrible skunk when your air conditioner is running, there may be gas leaking somewhere within the air conditioner. This gas is called methanethiol, and it has a smell much like a dead animal. The gas enters your home through the ductwork, and then circulates from room to room. The first thing you should do is to call the gas company, and then call your HVAC technician to clean your system.
Dirty Socks Smell
If your home smells like dirty socks when your air conditioner is on, your air conditioner may be too large for your home. While your HVAC system removes heat from the air in your home, it also dehumidifies, which is removing moisture from the air. If the HVAC unit is too large, it will not run long enough to remove all of the moisture from your home. When there is high humidity outside, the humidity builds up inside your home, and then mold and mildew will start growing inside of the HVAC unit's components. So this dirty sock smell you are smelling is actually mold and mildew.
Animals often try to find a cool place to go when the temperature goes up outside. One place they may go is underneath your home. When they do this, they can get inside of your air ducts. If they urinate while they are in there, your home will smell like urine.
You can start out by cleaning your vent cover. Use a screwdriver to remove the vent cover and pull it away from the wall. Fill a bottle with vinegar, add approximately two or three tablespoons of baking soda to the bottle, put the lid on, and shake it up. Spray the registers down this solution and then clean it off using a damp rag. Let the vent cover completely dry, and then put it back on.
You should also go ahead and change out or clean your air filter to make sure the smell is completely gone. Contact a professional like one from Century Heating & Air Conditioning Services for more information.