Common HVAC Odors & Causes

Common HVAC odors can range from unexpected to unpleasant to downright disgusting. Some can even point toward serious problems. Learn the causes and how to deal with them to avoid long term problems or immediate health hazards.

Musty, Moldy Stench

A moldy, mildew smell is among the most common HVAC odors you're likely to encounter. Not surprisingly, that smell indicates there is mold somewhere in your system. How did that happen?

An air conditioner dehumidifies your home, but that water has to go somewhere. A clogged drain and dirty coils can cause mold growth in the ducts, crawlspaces, or elsewhere. Your first step is to inspect the condensate drain. If it's clogged, that's likely the source of your problem. Clean it out, then clean the mold, and you're probably good. If the issue persists, contact an HVAC technician to check your system.

Rotten Eggs

Unless there is a sulfur mining operation in your backyard, the smell of rotten eggs is probably an unwelcome one. It's also one you should be immediately concerned about. Natural gas is odorless, but most providers put in a sulfur additive. If you smell that, it can mean there is a natural gas leak in your home.

Don't take chances! Open up the windows, and call your utility company immediately. The smell is there as a warning. Ignoring it could literally kill you.

Something's Burning

When you first turn on your heating system, do you detect a mild burning smell? If so, this is completely normal. Your heater has been sitting unused all summer, so some dust has built up on the interior mechanisms. It burns up quickly, and is nothing to worry about. The smell should go away in about half an hour or so.

But what if it doesn't go away? In that, case contact your HVAC technician. There could be a more serious problem. It's also a good idea to shut the unit off until it is serviced.

Any common HVAC odors we missed?

Have you noticed a weird smell in your home that we didn't mention and want to ask about it? Put your question in the comments below, ask via email, or on chat!

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