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Why Does My HVAC Smell Bad?

April 18, 2017

When HVAC Stinks…

There’s no denying our society’s love for air conditioning — it’s what allows us to live comfortably in beautifully sunny climates. The cool air moving through our homes is a welcomed bliss during hot summer months. But, what happens when that cool, refreshing air is also spreading a bad odor throughout your home? Unfortunately, air conditioners are prone to mildew, malfunctioning, and more.

Different odors point to different problems, which is why today we’re going to walk through the 5 most common reasons your air conditioner may smell bad:

Dirty Sock Smell

While we rely on air conditioners to cool our homes, it’s easy to forget these systems are also used to remove moisture (or, dehumidify). In some cases, a system may be too large for the home, causing it to move through its cooling cycles too fast. This opens up the possibility for moisture to remain in your home. On days where humidity is particularly strong, mold and mildew growth on air conditioner parts can push this stink, “dirty sock” smell throughout your home. Call an HVAC professional to assess whether your system is too large for your space; if so, an expert can help you adjust your system needs based on the size of your home.

Mildew or Dirty Feet Smell

As we mentioned above, air conditioners are prone to mold and fungus growth, which tend to cause the smell of mildew, or dirty feet. Clogged or dirty filters can cause this fungus growth, due to trapped organic particles being exposed to this moisture. Clogged condensate drain lines can also lead to moisture build-ups around the coils of the air conditioner. If your moist ducts aren’t sealed correctly, you may find mildew growing as a result. Drip pans that aren’t positioned properly — or are overflowing too fast — can accelerate this growth even more. Sometimes cleaning the clog around the drip pan is all it takes; though, professionals should be brought in for more serious issues.

Rotten Egg Smell

Of course, the smell of mildew is nothing compared to the rank smell of rotten eggs wafting through your home. If you’re experiencing this smell, it’s most likely due to a dead animal in your air duct. You probably haven’t done anything wrong — unfortunately, it’s not uncommon for an animal to climb inside a duct during the winter, and then pass away without anyone knowing. At the end of the winter season, when you restart your unit in the spring, the resulting odor can be a wakeup call for your home — and will require professionals for carcass removal. Talk about spring cleaning!

Skunk or Raw Sewage Smell

Surprisingly, although the “rotten egg” smell often correlates with animals, the recognizable scent of skunk could actually signal something more serious than a dead animal. Methyl mercaptan is a gas that smells a lot like a skunk’s icky spray, and could indicate a gas leak in your home.

Similarly, the smell of gas or sewage could indicate a sewage leak, or ruptured vent pipe near your system’s air duct. Both methyl mercaptan and methane are very dangerous to inhale — so if you whiff these smells, leave your home immediately and call an HVAC professional to deal with the issue.

Carbon, Gunpowder, or Exhaust Fume Smell

You may have frayed wires, a burned-out circuit board, or a burned out fan motor in your system — all three of these issues can produce the smell of carbon or gunpowder, rather than a traditional burning or smoke scent. If you notice the scent of exhaust, this signals that something other than water is leaking from your HVAC system (nothing except water should leak from your system). In either case, professionals should be contacted immediately.

Turn to the Experts

While homeowners can change air filters or drain drip pans on their own, sometimes this isn’t enough to remove smells from your home. Fortunately, all the issues listed above can be taken care of by HVAC experts, who know what to look for and how to safely deal with these problems within your system. You should already be scheduling professional maintenance on a regular basis, in which case many of these issues can be caught and prevented by your HVAC expert before they cause a real problem. While some smells indicate more serious danger than others, either way, there’s no reason to live inside a smelly home — so call a professional to get an expert solution, and you can go back to living amid cool, fresh, and clean air.

About The Author

Bob Jenson

For over 45 years, Bob Jenson has been providing quality heating and air services to the San Diego community.

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