12 Reasons Your AC Might Smell Bad

bad smell from ac unit

On a hot, muggy day there is nothing quite as refreshing as turning on the AC and feeling the blast of cool air. However, if the cold air isn’t so fresh smelling, you might have a big problem.

“What’s that smell,” you may ask yourself. Whether your air smells like rotten eggs or dirty socks, your air conditioning unit may need repair. Learn about the different smells you may encounter and explore these twelve reasons your AC might smell bad. Furthermore, learn when it’s time to call in a professional.

1. Mildew

As AC units cool your home, they also remove excess moisture from the air. If that moisture doesn’t drain properly, it’s likely that your air will smell like mildew. Replace your filter and, if necessary, have your air conditioners professionally cleaned.

2. Rotten eggs

If your air smells like rotten eggs, it’s likely that a critter (such as a bird or rodent) crawled into your duct during the winter to stay warm and then passed away. Having a professional remove the animal and clean the ducts should clear up the rotten smell.

3. Sewage

Unfortunately, sewage lines may back up. If that happens near a duct, even the smallest amount of methane gas can make your entire house quickly smell like sewage. Because methane gas is dangerous, call a professional HVAC technician immediately.

4. Stinky feet

Stagnant water and clogged AC units often emit a stinky feet smell. A proper cleaning should eliminate this smell.

5. Skunk

While the rotten egg smell of a decaying animal is not dangerous, a skunk smell does warn of immediate danger. A gas leak of methyl mercaptan, which smells like a skunk can then cycle through your ductwork. It is imperative to evacuate your house and call the gas company as well as an HVAC technician.

6. Gunpowder

The gunpowder smell is caused by either a circuit that shorted out or a fan motor in need of replacement. A technician should be able to look at your system and recommend which parts need to be replaced.

7. Exhaust fumes

Electricity powers air conditioners, but the motors do contain fluids that help perform. If any of these fluids leak out, you may detect a smell similar to exhaust fumes. This should be repaired as quickly as possible.

8. Burnt rubber

A problem with a fan or motor can cause a burnt rubber smell. If, at any point, you smell a burning odor, turn off your unit immediately to avoid the risk of a fire.

9. Mold

If mold has grown inside your vents or ducts, the air emitted from your vents will smell moldy. Mold growth can occur either because of a leaky duct, high humidity levels, or because mold growth elsewhere in the house has spread to the ducts. While duct cleaning is essential, you should also look for the cause of the problem to prevent the mold from reappearing after a cleaning.

10. Wet dog

Frequently, your AC may smell like a wet dog when the filter is past due for a change. If changing the filter doesn’t solve the problem, there are other possible causes including Dirty Sock Syndrome, mold, mildew, and actual pet hair.

11. Dirty socks

While it has nothing to do with real dirty socks, “Dirty Sock Syndrome” is a common cause of stinky air. As ice builds up due to frequent use in the hottest months, the wet area can attract mold and bacteria to the coils of the unit, which results in the dreaded dirty sock odor.

12. Pet hair

Pet hair, dust, and other contaminants can end up in your ducts. As contaminants build up, you may notice the air from your vents smelling like pet hair.

If you experience any of these odors, please contact us right away!