Time to change your AC filter? Scientists reveal the ammonia smell in your system comes from bacteria feeding on dead skin cells

Always trust your senses, especially when it comes to determining how potentially dangerous something can be. New data released from the Hong Kong Baptist University revealed that air conditioning units collect dead skin cells and then break them down into ammonium, releasing the acrid, sweet smell we’ve come to associate with urine. While not immediately dangerous, units that continually release ammonium into the air could make people more susceptible to disease and upper respiratory tract infections.

Dr. Lai Ka-man, who led the research, says that people should immediately change their air conditioner filter once they begin to detect the scent of ammonium. Dr. Ka-man explained that “skin squames,” which are dead skin cells that have peeled off the surface of the body, collect in the air conditioner filter. These squames then become the food source of bacteria that breed in the unit. The keratin found in the dead skin cells is broken down by enzymes called keratinases which produce ammonium. Consequently, a urine-like smell is released.

“For effective long-term odor control, it is important to reduce the amount of skin squames from entering the air-cooling units,” said Dr. Lai. “The simplest way is to install an appropriate filter to capture the skin squames in the air. A filter that can effectively capture particles less than [0.001 centimeters] should help improve the odor problem.”

Air conditioning maintenance

Air conditioning units have become a standard in offices, schools, and homes. For the most part, we don’t pay attention to them unless something really goes wrong. This lazy approach to air conditioning maintenance can lead to very dangerous health problems. When you do not regularly change your air conditioning filter, you and your family become more vulnerable to:


  • Respiratory problems – Air conditioning units are a fantastic breeding ground for various microorganisms and mold. Several studies on the matter have concluded that mold from air conditioning units can contribute to an increased risk of asthma, bronchitis, and other respiratory illnesses. Those with a compromised immune system are also in danger of developing severe lung infections and other reactions. Wheezing, coughing, and sniffling are the first warning signs you should take note of.
  • Contaminated air – Air conditioners “condition” the air. They DO NOT freshen it. Air is circulated at lower temperatures so that it becomes cooler. That said, there is an increased chance of spreading indoor pollutants such as bacteria, molds, mildew, and viruses. Make sure that you regularly let outdoor air in to reduce the amount of air pollutants found inside.
  • Diseases – Air conditioning units, especially centralized ones, can trap people into breathing the same air. If one person is sick with, say, bacterial pneumonia, and does not practice proper cleaning habits, that person can place everyone in the same space at risk of developing the condition as well.
  • Workplace illness – A recent study found that air conditioning units can contribute to the number and severity of employees getting sick. Cases were observed to worsen if the air conditioning unit was not regularly cleaned.

Each air conditioner manufacturer has their own set of guidelines on when you should have your unit checked. This ranges from having it checked every six months to every two years. Regardless, if you start to notice a funky smell coming from your unit, if it begins to make loud or strange noises, if the air flow is weak, or if your energy bill is way too high, it can be a sign that your air conditioning unit needs repair.

You can read more articles related to air quality at Environ.news.

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