Are you trying to figure out how to get rid of an odor coming from your air vents? If it seems like there is a smell in your home that gets worse when the heating or air conditioning is turned on, you can probably find out where the smell is coming from fixing it yourself. This article explains how to detect odors, and comprehensively get rid of them. As you will see, in some cases you will need to hire a professional to solve the problem.
Finding the Odor Through the Registers
Obviously, you want to start whatever the odor is the worst. If the air coming out of a certain vent seems to be especially smelly, it could be that something is causing the odor within that section of the duct system. It is very common for mold to form inside of ducts. Even worse, small rodents or birds can get stuck inside your duct system where they die. The air flowing past these small animals can be very strong. So, you need to remove your air registers from the walls and look inside your duct system using a flashlight. If you don't see any mold or animal carcasses, go to the next register.
You should thoroughly check every register and connected duct, even if you don't notice any smell in that area. Because of the way the air flows, the odor can be coming from anywhere within your duct system.
Check Your Major Appliances
Once you are done inspecting your air ducts, you should check your actual air conditioner and furnace. If the smell is more pronounced when your heat is turned on, then there is a greater chance that it is originating from within the furnace. First, check the state of your furnace filter, if it is moldy and dirty, you should replace it anyway, even if it doesn't actually smell. Now, you should inspect inside the actual furnace cabinet. If the odor is coming from the blower compartment, where the fan is, it will easily be able to tell because the smell should be very strong. If you have checked everything, and don't see any dead animals or mold buildup, now might be the time just to call in a professional. They will be able to give your duct system and more thorough cleaning using special camera systems. They can reach the small percentage of ducting that you are unable to see and access.
Having a company like Bourke's Service Co who knows exactly where to search might be your best bet for permanently getting rid of the odor.