## A breeding ground of bacteria Is it true that pathogenic microbes can live in air conditioning unit filters, including legionella bacteria, which causes a deadly infectious disease with pneumonia symptoms called Legionnaires' disease? Legionella was named after the participants in the American Legion Veterans Convention — they were its first known victims at the time. Of the more than 2,000 delegates at the 1976 forum in Philadelphia, Pennsylvania in the United States, 221 suddenly fell ill and 34 died as a result of an illness similar to pneumonia. The infamous forum was held at the swanky Bellevue-Stratford Hotel, whose air conditioning system was found to be the source of the mass infection. However, air conditioners have changed drastically since then. In particular, antibacterial filters are now used, which destroy pathogenic microbes. To keep an air conditioner clean, you should replace or clean the air filter regularly (usually every six months) and clean the air ducts annually. ## Air conditioners and COVID-19 Is there an increased risk of catching [COVID-19](https://ul.orna.me/KOge/librarydisease?id=221) through an air conditioner at work or home? According to experts, air conditioning systems do not pose any additional threat to health during a pandemic. The main negative factor here is the closed space and absence of fresh air from outside, which can be easily removed by opening up windows and doors at least twice a day. ## The source of stuffiness Most conditioners just blow air available into the area, creating only an illusion of fresh air. As a result, the area can feel stuffy — especially in places where there are a lot of people all the time. Newer air conditioners are equipped with more advanced filters that purify the air. More advanced ones even have ventilation functions. If the air conditioner does not have these features, the windows of the area can be opened periodically for fresh air. ## The cause of colds You can often hear complaints about people catching colds from air conditioners. Doctors attribute this to the sudden change in temperature when someone enters from the heat outside into a room with cooled air. This can be avoided by setting the temperature correctly. The temperature difference in the room and on the street should not exceed 8–10 °С. In addition, the device should be installed so that the airflow is not directed at people. ## Dust, mold, and allergies Some believe that dust and mold accumulate in filters of air conditioners, which can cause [allergy](https://ul.orna.me/KOge/librarydisease?id=21) attacks. This statement is only partly true, as modern conditioners have at least two filtering elements. The coarse filter catches the pet hair and fine dust. The fine filter catches mold spores, microbes, dust mites, pollen, and smoke. An air conditioner with clean filters does not pollute but cleans the air. If you follow the maintenance schedule of the unit, your air conditioner will not harm your health.