Toxic Car Syndrome: Mildew or Mold in your Car’s Air Conditioning

Health Risks from Mold in your Car’s Air-Conditioning

Is your vehicle making you sick? Is there mildew and mold in your car’s air conditioning? This can be especially noticeable right when you first turn it on. It’s a surprisingly common problem and it can impact your health, especially if you have mold allergies or sensitivities.

Many new vehicles have mold in their air conditioning.

An evaporator can become a source of mold in a car's air conditioning

If the evaporator from a car’s air conditioning is not working properly it can be the cause of toxic car syndrome.

Inside your vehicle’s air conditioning system, you have a part called an evaporator. This part is designed to remove both the heat from your vehicle’s interior (when the A/C is turned on, anyways) as well as remove any moisture from the air that’s being cooled. Even when the air seems pretty dry, there’s still enough moisture to cause condensation in your vehicle’s evaporator. When moisture condenses on the evaporator, it’s supposed to drip drain away. However, very often the drain will become clogged and/or it won’t drain quickly enough. If water can stagnate inside the evaporator unit, this water grows mold and mildew that causes your vehicle’s air conditioning system to smell — especially immediately after the system is first turned on.

Fixes for Toxic Car Syndrome: Cleaning the AC Evaporator

Fixing an automobile with toxic car syndrome can be challenging and expensive. Here are some tips from the pros to keep your AC running mold-free:

  • Some car manufacturers have put out advisories on the problem and have told mechanics how to fix the problem. Many times it involves a disinfectant sprayed into the ventilation system. Spraying disinfectant into the air vents won’t kill these growths.
  • The best solution is to clean out the evaporator. But since that’s such a time-consuming and expensive job you may want to try another option.
  • When you use the AC, there should be water draining from under the car. No water runoff means that the drain hole is blocked and the evaporator is not drying out, creating a perfect breeding ground for mildew.
  • Cooling Coil Coating and Clean ‘N Coat are commercially available products that work as a protective coating for the evaporator coils and fins.
  • Prevent mold in your car’s air conditioning from growing in the first place. Turn off your air conditioner five minutes before you stop driving  and then turn on your interior fan to full speed. This helps dry out your vehicle’s AC system. Just five minutes on fan (without using AC) before you shut your vehicle off will make a difference.
  • Air-conditioning should be run on the “outside air” setting, as opposed to the recirculated setting as often as possible. This allows the system to pull in new air and get rid of old moisture. The “max” setting is going to give you recirculated air and should only be used on brutally hot days and only until you get comfortable.
  • Never leave the AC set on “max” while the engine is off. This keeps the vents closed and doesn’t allow outside air to get in. The heat created by a closed system combined with the moisture produces a virtual greenhouse for mold.

For more on your car’s air conditioning system refer to the Mobile Air Conditioning Society (MACS)


  1. Air Conditioner Covers says

    The amount of refrigerant used in an air conditioning unit determines whether the makers would get the highest SEER level of efficiency or not–the lesser, the better. The units are designed in perfect balance, and so the slightest hindrance to the heat transfer usually conks out the balance and deteriorates the functioning of the unit. If dust or dirt accumulates on the coils, the right amount of heat doesn’t go out, thus increasing the temperature and pressure of the refrigerant going into the compressor to abnormal degrees.