A: That is a very common issue and there’s a thing called “The Dirty Sock Syndrome.” Believe it or not, that’s what they call it, where bacteria will build up in the evaporator coil. A lot of the time it will go dormant and will be reactivated once moisture is introduced. When the system comes on, it gives off a foul smell.
Sometimes, the evaporator coil can be cleaned with a special product. However, if the bacteria is too deep into the pores of the metal; the fins of the coil, sometimes you have to replace the evaporator coil. It depends on how severe the issue is.
Have you ever come home from work after a typical humid Houston day just exhausted from the summer heat? You walk in get comfortable and crank the AC down to 72° to get some relief and then—it hits you. The nastiest smell that takes you back to your high school locker room.
It reeks of a combination of sweaty socks, hot garbage, and burning dust—we have your attention now? Yeah, so you immediately rush to turn the AC off and sit there holding your nose wondering why your air conditioner smells bad.
Then the worry sets in, you start to go full, worst-case scenario. Imagining a $2,000 repair or worse, having to replace your HVAC. Well, don’t get ahead of yourself—if your air conditioner smells foul, it may not necessarily be something major.
My Air Conditioner Smells Like…
We’ll cover a few common problems that could make your air conditioner have a foul odor. It could smell like a mildewy sock, burning dust, or even smell like smoke. Regardless of what it is, we’ll give you some insight so that if this ever happens to you—you’ll be prepared.
Exhaust Fumes From A Car
Obviously, air conditioners don’t run on gasoline or have an engine. However, if your air conditioner smells like a ’67 Mustang with no muffler, there’s a rational explanation. While there is no gasoline, an HVAC unit does use some fluids such as refrigerant. When refrigerant, for example, gets hot— it can smell like a car’s exhaust. When you have a smell like this, it’s typically indicative of a refrigerant line leak. Not only can a refrigerant damper the performance of your AC unit, but it allows hazardous chemicals to be released into the environment.
If your air conditioner is giving off this smell, it needs to be checked by a professional ASAP. In some situations, a leak can be much more dangerous. So, you need a certified technician to repair the issue, and in the meantime, be sure to air out your home and keep it ventilated.
Something Is Burning
HVAC systems contain a lot of electrical components such as power boards, fans, wires, and more. If your air conditioner smells like burning plastic, or gun smoke—chances are one of these components is burning. In this scenario, you want to turn your AC off immediately and contact an HVAC technician.
Never attempt to diagnose or repair an electrical issue with your unit on your own. There’s extremely high voltage built up in those components and one wrong move could kill you.
Now, if your air conditioner just smells like a regular burning scent and not like plastic, there’s another logical reason. If your AC has not been used in a while, dust can accumulate in your unit. When you turn on the AC, the dust burns off for a quick second and gives off a burning smell. If the smell is temporary, that’s likely all it is and is nothing to be worried about. However, if you wanted to be sure you should become an AirTeam MVP member and have your AC serviced regularly.
Rotten Eggs Or Other Nauseating Smell
Ever turn on your AC and immediately hit with a nauseating smell like rotten eggs—SPOILER ALERT— it’s usually not eggs. It’s usually a dead mouse, bird, or some other creature that got stuck in your system.
It’s a smell that is distinctly pungent and unique and you can’t confuse it for anything else. It could’ve been caught up in the blower fan, a duct, or somewhere else in your attic. Over time, the carcass begins to smell bad, especially in hot months. With mini-split systems, lizards and other creatures can make their way into your indoor blower as well.
A good practice to have is to make your system critter-proof to avoid such a foul scenario. A qualified HVAC technician can usually remove the animal, or you can remove it yourself. If it’s in the attic but not the duct, some kitty litter sprinkled around will help deodorize. If it’s within the duct, it will need to be disinfected or replaced if damaged.
You will need to determine the duct that the smell is coming from and use a screwdriver to take off the cover. Then, remove the carcass, disinfect and make sure to wipe the surface dry before putting the cover back on. It’s always a good idea to call an HVAC technician to make sure there’s no further damage within the ductwork in the attic.
Natural Gas Or A Skunk
If you smell natural gas or a skunk-like musk it’s a potentially dangerous situation that needs immediate attention. That’s because you’re probably not smelling either of those, rather you’re likely smelling methyl mercaptan. Natural gas has no odor on its own, the gas company adds methyl mercaptan to the supply for safety. Without this additive’s distinct and foul smell, you’d never know there was a natural gas leak until it’s too late.
So, that being said, if your AC smells like this, it means there’s a gas leakage somewhere in the system. The first thing you should do is shut off the gas supply to your home. Then contact your utility company who will determine the source of the leak and repair it.
Must Or Mildew
This is the most common smell we get calls about from our customers. When an air conditioner smells like this, it’s normally an accumulation of water in the ducts or drain pan. That stagnant water is a breeding ground for fungus and mildew to grow.
However, if it’s not that it’s usually really dirty filters, especially in a humid climate zone like Houston. With our humidity here, dirty filters can absorb a lot of moisture, and then mildew sets in and causes the smell.
The good news is that it’s easily preventable—change your filters regularly. If you have an advanced MERV system that is harder to access, call an HVAC technician. Has it been a long time since you’ve changed the filters? If so, then you should go ahead and have the ducts cleaned as well.
If Your Air Conditioner Smells Bad Be Careful Of DIY Solutions
It’s normal to want to fix these problems yourself since some of the causes can be fixed by yourself. However, there are some things to consider before attempting a DIY fix. If it involves touching any of the equipment—STOP. Call a professional, as you could do more damage to your system or electrocute yourself.
That being said, if it’s something like a dirty filter or something in the duct that’s easily solved and cleansed—that’s ok. Just make sure you are familiar with what you are doing so that you don’t damage your ductwork.
Also, on the opposite end of the spectrum don’t NOT take action and try and mask the smell. Too often we get customers that cover it up with incense, spray Febreeze, etc. This only delays any repairs that your HVAC system may desperately need. Usually, a smell is a sign of an inexpensive repair that needs to be done.
Ignoring the minor issue can cause it to escalate to a much larger issue and thus more costly. Bottom line is, when there’s a problem, resolve it as soon as possible.
AirTeam’s MVP Program Can Help!
You can avoid most surprise issues with your air conditioner by enrolling in our MVP preventative maintenance program. Our technicians keep your system in top form with regular service calls, filter changes, and tune-ups.
Contact us today to sign up for this valuable service and keep your system running great for years.