The hidden health risks of air conditioning in the car: advice from a chief physician

Very few people go to the bother of having their car’s air conditioning system maintained and disinfected regularly. Yet this is precisely where some potentially dangerous unwanted passengers may be lurking.
You are here:

Healthy holidays with TCS and Well

In this episode, you will learn why car air conditioners can be a health hazard. Prof. Dr. med. Aristomenis Exadaktylos, Chief Physician and Clinical Director of the Department of Emergency Medicine at the University Hospital of Bern (Inselspital Bern), also answers questions about humidifier lung.

You can find additional interesting health tips at

Preventing humidifier lung

Because a car or motorhome’s air conditioning system is used so often, it also needs to be maintained regularly. Convincing proof of this is provided by the results of a microbiological analysis carried out by the Institut IBO für Innenraumanalytik (IBO Institute for Indoor Analytics). The Institute’s researchers tested the filter of a car’s air conditioning system that had not undergone any maintenance for five years. In that time, the filter had accumulated 600,000 living bacteria, 350,000 living fungi and tens of thousands of living yeasts.

One of the most surprising findings was the presence of microorganisms that usually live at a temperature of around 37 degrees Celsius – body temperature. So if you are getting a musty smell from your air conditioning system, you should take your car in for servicing as soon as possible. That smell indicates that the system is circulating unfiltered pathogens around the vehicle’s interior, and you are inhaling them.

When this happens, some people have an allergic reaction that involves inflammation of the alveoli in the lungs, and they can develop “humidifier lung”, a condition whose symptoms include fever, dry cough and increasing shortness of breath.

Air conditioning systems are not maintenance-free
Regular maintenance is essential to ensure that an air conditioning system functions properly in the long term. An air conditioning service involves checking the functions of the most important components of the system such as the compressor (also known as the aircon pump), condenser, evaporator and expansion valve. Tubes and seals can also age or dry out and become leaky as a result. For this reason, manufacturers advise an annual inspection of the air conditioning system at a specialist garage. Spring is a good time for an air conditioning service – just before the warm summer season when the air conditioning system has to work at full capacity again.

Interview with Prof. Dr. med. Aristomenis Exadaktylos

Prof. Dr. med. Aristomenis Exadaktylos

It is usually the upper respiratory tract and the lungs that are affected.

Prof. Dr. med. Aristomenis Exadaktylos
Chief Physician and Clinical Director of the Department of Emergency Medicine at the University Hospital of Bern (Inselspital Bern)

How is humidifier lung treated?
If an infection occurs, it is usually the upper respiratory tract and the lungs that are affected. However, it’s not always easy to make the connection. In complicated cases, the treatment may involve antibiotics, for example. Modern vehicles are usually well maintained, but care should be taken when driving older vehicles or rental cars abroad where there is an obvious backlog of maintenance work needing to be done.

Can humidifier lung be fatal?
I am not aware of any case where it was. However, all kinds of highly pathogenic organisms have been detected in air conditioning systems. The reason for this is that condensation forms on the surface of the air conditioning evaporator that is responsible for cooling the intake air and simultaneously cleaning and dehumidifying it. This condensation mixes with dust and dirt, creating a paradise for all kinds of microorganisms. Here’s what my car mechanic recommended to me: before you turn off the vehicle, switch off the air conditioner for a few minutes so that the evaporator can dry out and fewer deposits can accumulate.
Are children more often affected than adults?

Children generally have more sensitive respiratory tracts and are therefore more susceptible to infections, and even to common colds caused by the air conditioning temperature in the car being too low. Special care should be taken when the temperature is very hot outside and very cold inside the vehicle. Air conditioners without digital temperature controls will often lead people to set temperatures that are colder than the 22 to 24 degrees recommended by doctors. Young children can react poorly to large temperature fluctuations.

When is it necessary to go to the emergency department or to the doctor?
With children, it’s better to act sooner rather than later if you suspect something is wrong, especially when they have a severe cough, fever or difficulty breathing. Allergies can also be triggered or aggravated by dirty air conditioning filters, causing further complications. The cause here could be anything from pollen to dust.

Would it be healthier to do without air conditioning in a car or motorhome?
No, definitely not. A vehicle’s air conditioning system is as important as its ABS or airbags. In fact, it’s like an airbag that cushions you against excessive temperatures. Accident researchers have found that when the interior temperature exceeds 37 degrees Celsius, the risk of an accident increases by a third compared to the ideal temperature. This is because excessive heat impairs attention and reactions. The effect corresponds to the impairment that would be caused by a blood alcohol concentration of 0.5% to 0.8%. Because keeping a vehicle’s interior at the right temperature is so important, if you are renting a car in hot southern climates, I would recommend staying away from poorly maintained cars, or at least testing the air conditioning before hiring a car, and if it smells “musty”, then you should definitely ask for a different car.

This contribution was made available to us by

The TCS recommends having the air conditioning system checked on a regular basis. 

Article posted by Well-Redaktion

On 29.06.2022

Share this article



Those articles may interest you

How to protect and care for your eyes properly - even on holiday

In the summer, exposure to pollen, chlorinated water and heat can be tough on our eyes. In addition, intense sunlight can burn the corneas of the eyes. What do you have to consider?

14.06.2022 - Well-Redaktion

Bildschirmfoto 2021 12 14 um 13.43.59
Galenica and AEVIS VICTORIA take stakes in the Well digital health platform

As shareholders, Galenica and AEVIS will play leading roles in the further expansion of Well together with its four founding partners: CSS, Medi24, Visana and the Zur Rose Group.

07.06.2022 - Well-Redaktion

foto 44
Well begins national roll-out: the future for Swiss healthcare

At a media event today, the national roll-out was announced: Well and its founding partners are leading a communication drive and rolling out an extended range of services to a wider public.

04.05.2022 - Well-Redaktion

iStock 1315599813
Partnership with Réseau Delta in French-speaking Switzerland

Well is now working in partnership with Réseau Delta, the largest managed care network in French-speaking Switzerland. For Well this marks another important step towards the digitalisation and integrated networking of the Swiss healthcare system.

26.04.2022 - Well-Redaktion