Air Conditioner Smells like Cat Pee: Causes and Fixes

It may sound funny to say you perceive cat pee in the house – when you don’t have a pet cat – but this odor perception can actually be correct if you run an air-conditioner to improve your indoor air quality.

With your air conditioning unit switched on, a urine smell can also be perceived as ammonia – but this doesn’t mean your baby or pet peed in the house, it actually means there’s something wrong with your air conditioning unit.

air conditioner smells like cat pee

Why Your Air Conditioner Smells Like Cat Pee

Now, let’s explain why your AC appliance emits smells detectable as cat pee or ammonia.

If you detect a urine smell in your indoor air while your AC is working, it indicates that there is mold growing in your unit or its ductwork. It is not really the mold smelling out, but the mycotoxins released into the air by the mold. You will need a professional to check and repair the problem.

Air Conditioner Smells Like Cat Pee: How to Fix

Here are ways to fix your air conditioner’s bad smells after identifying the causes of indoor air pollution. You may possibly be able to do some of the required tasks to remove the smell from your AC, and you may have to contact a professional technician to help in certain cases.

But all things being equal, it is best to carry out routine and preventative maintenance on your unit twice a year in order to avoid breakdowns and costly repairs.

On your own part, here are some of the things you can do to prevent or fix smell issues with your air conditioner unit:

  • Use wipes and liquid solutions to clean your unit – not cleaning sprays
  • Ensure your pets do not shed their hair or paws near the unit
  • Temporarily use deodorants to reduce indoor air pollution while you call the technician
  • You may also open all doors and windows for proper ventilation while the technician is on his way
  • Invest in high-quality air filters and other HVAC components
  • Get your unit cleaned and serviced regularly by a licensed professional

Depending on the cause of the indoor air smell or possible unit breakdown, your local repairman will be able to –

  • Clean out clogged components and other blockages
  • Lubricate moving parts for efficient functioning
  • Tune-up wiring, harnesses, and other parts
  • Repair and replace malfunctioned components
  • Prevent a reoccurrence of the fault

Other Bad Smells from Air Conditioners and Their Causes

Let’s now consider other distinguishable bad smells from your air conditioner and what each indicates, as well as how to fix them.

  • Smell of burning plastic in the house

If you perceive the smell of fish or burning plastic in the house while your AC unit is on, it means the motor in the unit is overheating due to a broken capacitor; there is little to no lubrication in the motor; the fan belt is damaged, or there are electrical malfunctions.

  • Smell of vinegar in the home

If you perceive a pungent smell like vinegar or mildew, the problem with your air unit could be a clogged air filter, moldy ductwork, excessive condensation, burned electric motor, and blocked pipeline among others. Clearing the drain pipe to remove blockage will solve the problem.

  • Smell of gas or rotten eggs

If you smell rotten eggs emitting from your air-conditioning unit, there is the likelihood that small animals like rodents crawled into the duct of the unit and died there. The decomposing body will definitely smell like rotten eggs. However, if the smell is like gas, you may have a gas leak somewhere in your house – natural gas has no smell, but manufacturers add additives (Methyl Mercaptan) to make humans detect a leak in time; some people said the additive in gas smells like skunk.

  • Smell of paint thinner

To some people, a paint thinner may smell sweet, but it is a bad thing when it is emitting from your air conditioner. This chemical smell indicates that your AC unit is having a refrigerant leak; this leakage means that the gas that is supposed to keep your unit cool through its copper coils is seeping out into the house. You will need a repairman to fix this problem.

  • Musty smell through the house

Also known as dirty sock syndrome, you experience a musty smell when there is a buildup of bacteria, mildew, and mold on the evaporator coil of your AC unit. You perceive a smell as if there are very dirty socks in the room, or as if someone just removed their feet from dirty shoes. Apart from filthy evaporator coils, poor water drain can also cause the smell since the drain pans become very dirty.

Changing the air filter and drain system as well as cleaning the coil will resolve the problem.

  • Smell of smoke or burns

If you perceive the smell of something burning or similar to smoke, it is likely that the electrical components of your air conditioner are burning. If you have not used your AC for a very long time, switching it on may produce the smell since residual dust will likely burn off as it heats up. But you must call the technician if the smoke smell persists since a fire hazard may result.

  • Other kinds of bad AC smells

Other kinds of smells that may emit from your AC unit include those similar to car exhaust, gunpowder, sulfur, and organic waste among others.


There is no denying the fact that smelly indoor air can be pollution from the air conditioner, but noting the above eye-openers and addressing them will improve your indoor ventilation until the technician arrives.

So air conditioner giving off a cat pee smell can be discomfiting, but your repairman will get the issue resolved without costing you too much. However, it is best to adopt routine and preventative maintenance to care for your unit and avoid embarrassing smells.

If you are ever in any doubt about the source and nature of the smells coming from your AC unit, be sure to speak to an accredited and licensed professional for assistance.