As a business owner, you rely on your commercial air conditioner to keep your employees comfortable and your customers satisfied. But what do you do when your AC starts emitting an unpleasant smell?

There are a few possible explanations for why your commercial air conditioner might be producing a bad odor. In this blog post, we’ll discuss some of the most common causes of foul-smelling AC and what you can do to fix the problem.

Poor Airflow

One possible reason for a foul smell coming from your AC is that the unit is not receiving enough airflow. When an AC unit doesn’t have enough air flowing over the evaporator coils, the coils can become ice-covered or frosty. This can cause a musty smell to come from the unit.

If you suspect that your AC unit isn’t receiving enough airflow, the first thing you should do is check the air filters. If the filters are clogged, they will restrict airflow and can cause the coils to become ice-covered. Be sure to call a professional to check the filters and clean or replace them as needed.

Your commercial AC technician may also check the vents and registers to make sure they are open and not obstructed. If they find that the vents are blocked, they’ll need to clear them so that air can flow freely into the AC unit.

Dirty Coils

Another possible reason for a foul smell coming from your air conditioner is dirty coils.

The evaporator coils and condenser coils can become coated with dust, dirt, and debris over time. When the coils are dirty, they can’t effectively transfer heat, which can cause the AC unit to work harder than necessary. In the process, the dirt and debris on the coils can produce a musty smell.

To clean the coils, you’ll need to call a professional AC technician. They will remove the coils and clean them with a special solution that will remove all of the dirt and debris. Once the coils are clean, they’ll be able to transfer heat more effectively, and the musty smell should go away.

Mold or Mildew

When mold or mildew strikes, it can cause a musty or earthy smell to come from your air conditioner. Mold and mildew can grow on the evaporator coils, in the drain pan, or in other areas of the AC unit.

This can be a serious problem because mold and mildew can cause health problems for you and your employees. As a result, it’s crucial to have your AC unit inspected by a professional on a regular basis to ensure that mold and mildew are not present.

If mold or mildew is found in your AC unit, the contaminated areas will need to be cleaned and treated. This is best done by a professional who has experience dealing with mold and mildew in commercial AC units.

Dirty Sump Pump

A sump pump is responsible for draining water away from the AC unit. If your commercial AC unit has a sump pump, it can become clogged with dirt and debris over time.

When the sump pump is clogged, it can’t effectively remove water from the AC unit. As a result, water can build up and cause a musty smell.

To clean the sump pump, you’ll need to call a professional AC technician. They will disassemble the sump pump and clean it with a special solution that will remove all of the dirt and debris.

Leaking Refrigerant

Refrigerant is a key component of your air conditioner. It helps to transfer heat and keep your AC unit running smoothly. But sometimes, refrigerant can leak from the AC unit.

If your AC unit is leaking refrigerant, it can cause a foul smell to come from the unit. You may be able to distinguish this smell by its sweet aroma.

Inhaling leaking refrigerant can be harmful to the health of anyone in your building, so it’s important to call a professional AC technician right away if you suspect your unit is leaking.


If you’ve noticed a foul smell coming from your commercial AC unit, it’s vital to have it inspected by a professional. There are several possible causes of the smell, and some of them can be serious.

At Affordable Service Solutions Heating & Air Conditioning, we have over a decade of experience installing, maintaining, and repairing commercial AC units in Richmond, Kentucky. If you are ever unsure about the condition of your AC unit, or if you just want peace of mind, give us a call. We would be happy to perform a maintenance check, where we can quickly diagnose the problem and recommend the best course of action.

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