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6 AC Smells You Shouldn’t Ignore

July 18, 2022 | Blog

When your air conditioner is producing bad smells, it can get to the point that you’ll opt for shutting it off and enduring the heat. If your unit smells, you might wonder why and whether it’s concerning. Whether your AC smells musty or like a carcass, you can’t fix it until you know more about it.

As AC odors are a serious problem, your Corpus Christi AC company, Mathews CCAC,  has compiled a list of 6 smells you can’t ignore.

Car Exhaust Smell


Air conditioners don’t run on internal combustion engines, and, therefore, shouldn’t smell like them. They do, however, use fluids that smell like this when heated. Feel like you’re standing behind a car? You might have a refrigerant leak. Used as a cooling agent, refrigerant leaks impact how units perform and release chemicals into the air.


A chlorofluorocarbon used in AC systems, Freon, absorbs indoor heat and releases it outside. Smelling like chloroform, or sweetish car coolant, Freon, while mostly odorless, is still detectable. Heavier than air, it doesn’t linger for long, quickly dropping down to floor level.

Though it won’t make you instantly pass out, this chloroform-scented leak is still dangerous.


Chemical-like smells require professional air conditioning maintenance as soon as possible. Before the professionals arrive, keep the smells out and prevent dangerous circumstances by cracking open windows and keeping your home ventilated.

Smelling Smoke Or Fire

Air conditioners have multiple electrical components including circuit boards, power wires, fans and compressors. Smelling burning gunpowder or plastic means that one, or multiple, components are, well, burning. Fixing this situation yourself would be extremely dangerous, instead, turn off your AC and consult a professional.

A common, less dangerous reason for smelling something burning is dust settlement in units after long periods of inactivity. The result? The accumulated dust inside your AC burns, producing bad smells when the unit is turned on. This, however, is temporary and not overly concerning.


If the smell remains or becomes pungent, or the air conditioning unit starts malfunctioning, turn it off and call your local HVAC expert.

Rotten Egg Smell

Air conditioners that smell like rotten eggs are caused by dead animals caught within the unit. Distinct and unmistakable, this odor will be sent throughout your entire home as soon as you turn the unit on.

Additionally, animals could also nest in ductwork, getting trapped and possibly damaging the system. Pest-proof the unit to prevent this and, if an animal’s stuck, remove it yourself or call a technician to do so.


Locate the duct the smell’s coming from, remove the cover with a screwdriver and extract the animal. Keep a light source nearby in case the culprit isn’t easily visible. Clean and dry the area, have your ductwork checked for damage and seal any entries.

Smelling Gas Or Skunk Spray

The most alarming smell produced within ACs is gas or skunk spray. Though natural gas is odorless, Methyl Mercaptan is added during air conditioner production. When gas is leaking and getting into your ductwork, this added chemical provides a pungent odor and ensures the problem’s detected before damage occurs.


Like rotten eggs, the smell of blinding skunk spray can’t be mistaken for anything else. At the first signs, turn off your gas supply and contact your utility provider to have them detect and repair the problem.

Moldy, Dusty ACs

When an AC smells musty, it’s often because of dirty filters, dust in ducted systems or water accumulation in drain pans or drip lines. Water causes fungus and mildew development, resulting in a foul smell. Turning on your AC after a long period while living in a hot, humid climate allows moisture accumulation within your filters.


Indoor ductless units give visible signs such as water dripping down walls when there’s a leak. Contact a professional and get your lines and ducts thoroughly cleaned and leaks fixed.

Cigarette Smells

If you, or anyone in your household, smokes at home your unit could eventually smell like stale cigarette smoke. This is unpleasant and can cause allergic reactions and headaches.

How does this happen though? Well, evaporator coils and filters absorb the odor of cigarettes, knocking loose embedded tobacco particles and sending them back into the home through the vents.


Thankfully, the solution to this is very simple: regularly clean your AC and change your air filter every 30-60 days. Additionally, smoking outdoors prevents the unit from absorbing more tobacco.

Getting Rid Of Pungent AC Odors

Even when you have found what is causing your AC odors, it’s not recommended to do AC repairs by yourself. If you feel confident attempting a DIY, go through maintenance and operating manuals and collect the tools you’ll need.

If you need professional AC maintenance, contact the professionals at Mathews CCAC today and finally breathe cool, odorless air again.

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