Aug 12, 2025 12:00:00

Poorly maintained air conditioners spread bacteria and chemicals, causing 'sick building syndrome.'

While air conditioning is essential for surviving hot summer days, it can sometimes cause a group of symptoms known as '

sick building syndrome .' Primrose Freestone , an associate professor of clinical microbiology at the University of Leicester in the UK, explains why air conditioners cause sick building syndrome and what can be done to prevent it.

Can air conditioning really make you sick? A microbiologist explains
https://theconversation.com/can-air-conditioning-really-make-you-sick-a-microbiologist-explains-260648

Sick building syndrome is a general term for symptoms such as headache, dizziness, fatigue, stuffy nose, cough, and rash that occur when staying in certain buildings. It is generally believed to be caused by chemicals used in newly built homes, but it can also be caused by staying in air-conditioned offices or hospitals for long periods of time.

A study conducted in India compared 200 healthy adults who worked 6-8 hours a day in air-conditioned offices with 200 healthy adults who worked in offices without air conditioning. The results showed that the group who worked in air-conditioned offices experienced more sick building syndrome symptoms over the two-year study period, with a particularly high prevalence of allergies. The study also reported that people who worked in air-conditioned offices had reduced lung function and a higher rate of absenteeism. Other studies have also confirmed that people who work in air-conditioned offices have a higher incidence of sick building syndrome.

One of the reasons why air conditioners can cause sick building syndrome is thought to be due to malfunctioning air conditioners. When an air conditioner isn't working properly, allergens, chemicals, and airborne microorganisms that would normally be trapped by filters are released into the air, Freestone said.

Faulty air conditioners can also release chemical vapors from cleaning agents and refrigerants into buildings, including

benzene , formaldehyde , and toluene , which are harmful and can irritate the respiratory system.

Poorly maintained air conditioners also pose a risk of harboring pathogens such as Legionella pneumophila , which can thrive in moist environments like bathtubs and air conditioners, causing Legionnaires' disease , which can cause pneumonia- and flu-like symptoms and can be life-threatening.

Research on hospital ventilation systems has shown that fungi such as Aspergillus , Penicillium , and Cladosporium , which thrive in moist environments, are more likely to thrive in air conditioners. Infections caused by these fungi can cause serious illness in people with weakened immune systems and premature infants.

There have also been reports of norovirus outbreaks in kindergartens in China due to air conditioners installed in the restrooms. Norovirus is usually transmitted through contact with infected people or contaminated surfaces, but in this case, it is believed that aerosols containing norovirus were spread by the air conditioner, infecting many children.

Another reason why air conditioners increase the risk of infection is that they lower the humidity inside the room, making it drier than the air outside. It is known that if you stay in a low-humidity environment for a long period of time, the mucous membranes of your nose and throat will dry out, reducing your ability to prevent the invasion of bacteria and other pathogens.

While poorly maintained air conditioners can cause sick building syndrome, properly maintained air conditioners have also been shown to prevent the spread of airborne viruses, including the new coronavirus.

'Air conditioners are designed to filter airborne pollutants, mold spores, bacteria, and viruses, preventing them from entering the air inside your home. However, this protection is reduced when filters become worn or dirty, or when the system is not properly cleaned. Proper air conditioner maintenance is essential to preventing air conditioner-related infections,' Freestone said.