4 Common Types of AC Odors and Their Causes

4 Common Types of AC Odors and Their Causes

A well-functioning air conditioner pushes odor-free air into your home. If a foul smell emanates from the vents in your home, something is likely wrong with your AC unit, and you need an HVAC expert to check it out. Explore some common types of air conditioner smells below.

Car's Exhaust

The AC unit, unlike a vehicle, has no internal combustion engine. As such, a cooling system that smells like a car’s exhaust when it runs is reason enough to worry. Exhaust fumes occur if fluids leak from your air conditioner, so consult an air conditioner technician immediately.

A refrigerant leak is likely the cause of the odor as it releases chemicals into the air. The refrigerant is a chemical compound that runs through your AC system, absorbing heat and providing cool air along the way. You don’t have to replenish this compound as with the oil in your car, and the AC unit should maintain the same quantity of refrigerant.

However, cracks in coils or the refrigerant line let the refrigerant escape and release chemicals into your home. Although it’s almost odorless, a refrigerant leak emits a sweet chloroform-like smell. Open the windows as soon as you detect chemical smells, and let an air conditioner expert assess your cooling system.

Rotten Eggs

A dead insect or animal stuck in some part of the cooling system is typically the reason for a foul odor. Birds, possums, lizards, and mice are among the critters that love to explore the ductwork, and a dead insect emits a rotten smell within days that worsens when you turn on the AC system.

While you can use a flashlight to search for the culprit, the chances are that the animal is deep within the ductwork. So, get an air conditioner technician to locate and remove the animal and check if entry points or other components sustained damage.

A rotten or skunk smell can also indicate a natural gas leak, in which case you require emergency air conditioner services. Natural gas distributors inject mercaptans and odorant blends to give the otherwise odorless gas a distinct smell. This odorization is a necessary safety measure because the gas is highly combustible.

If the odor from your cooling unit smells like skunk spray, quickly turn off your gas supply and get everyone out of the house. Then, contact your utility provider to assess the issue.


A burning smell from your AC unit is unmistakable, indicating a problem with an electrical component. An AC system has numerous electrical elements, such as the capacitor, fan motor, pressure switches, circuit boards, fans, and compressors.

A burning odor can mean an overheating fan motor, a broken fan belt, or a buildup of dust. If the smell dissipates after a few minutes, you probably have nothing to worry about, as your unit may only be burning off dust. However, have an air conditioner expert examine your cooling system if the burning odor lingers to prevent fire.

Musty Smell

Many homeowners consult AC system experts to fix a musty smell, which has a couple of potential causes. Most likely, mold and mildew have overrun your ducts, due to dirty and moist air conditioning components.

Bacterial and mold growth is especially common in the drip pan, drain line, and evaporator coil, as blockages cause water to accumulate. An AC unit cleaning service is the best way to clean a moldy air conditioner and eliminate musty smells.

If you don’t change the AC unit’s filter, moisture buildup also encourages mold growth. If you reside in a hot and humid area and operate your AC system infrequently, swap the filter before turning on the cooling system.

If your AC unit pushes out a musty, rotten, burning, or chemical smell, our cooling experts at Baton Rouge Air Conditioning and Heating will diagnose the failing component. Contact us today to enjoy an odor-free home.

Recent Posts

HVAC Maintenance

A Comprehensive Guide to HVAC Maintenance for Baton Rouge Homeowners

Located along the banks of the Mississippi River, Baton Rouge is a vibrant city filled with rich culture, history, and a strong sense of community. ...

Read More

Why Dehumidifiers are Essential for Port Allen Homes: Maintaining Comfort and Indoor Air Quality

Located along the west bank of the Mississippi River, Port Allen is a charming city known for its rich history, vibrant culture, and close-knit community. ...

Read More
Heat Pump Tune-Up

Comprehensive Guide on Heat Pump Tune-Ups for Port Allen Homeowners

Ensuring your home or business in Baker, LA is both comfortable and energy-efficient is crucial, and the role of a dependable heating system in achieving ...

Read More