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legionella bacteria

Beware of diseases transmitted by unsanitary air-conditioning systems

Regular maintenance of heating and air conditioning systems is hugely important, as badly maintained or badly designed air-conditioning systems are a ticking time bomb. Left unchecked, the system could become contaminated with harmful bacteria or fungal spores. These will then be disseminated by the same system designed to filter the air in a home, office, or car. These can give rise to particularly dangerous and even deadly conditions – these next four are amongst the most common.

Respiratory tract infections

Poorly maintained air-conditioning systems can cause respiratory tract infections, such as the common cold, flu, tonsillitis, coughs, and everything in between. Dirty filters are the most common culprits. Filters in an air-con system are there to remove bacteria and other contaminants. If they are not replaced regularly, the system allows airborne bacteria and viruses to circulate freely. So, when Tom from accounts staggers into the office with a heavy cold because he can’t bear to let the boss down, he unwittingly passes on his cold to everyone else in the building.


Legionnaire’s Disease affects around 500 people in the UK each year. The bacteria are transmitted via water-borne droplets from contaminated cooling towers. Make no mistake, the Legionella bacterium is deadly because it can cause pneumonia in affected patients. Patients with a compromised immune system or lung disease are the most vulnerable. Legionnaire’s Disease is spread by air-conditioning systems, among other things. The mortality rate is about 10%, which means that for every ten people who develop Legionnaire’s Disease, one of them will die.

Black mould

black mould

There are many different types of fungi, some of them safe, others less so. Black mould, or to give it its scientific name, Stachybotrys chartarum, is one of the deadliest forms of fungi. Under the right conditions, fungi like black mould produce deadly mycotoxins. Exposure to black mould mycotoxins can cause lung damage and long-term health problems.

Mould contamination in unclean air-conditioning ducts is a major health issue. Systems should be maintained and cleaned regularly, with filters replaced to prevent black mould spores from being circulated around the building.

Sick building syndrome

Sick building syndrome was first identified in the 70s and 80s, by researchers investigating health problems experienced by people working in office buildings. Seemingly unrelated health problems such as respiratory infections, general aches and pains, and a vague feeling of being ‘unwell’ have been linked to badly maintained air-conditioning systems.

People with low immune systems often report throat irritation, tightness in the chest, a perpetually runny nose, itchy eyes, skin rashes, headaches, and other non-serious problems. This can cause increased employee absenteeism and a loss in productivity, which is not good for businesses.

The cause is a build-up of bacteria, viruses, toxins, and allergens in the air-conditioning system, which is transmitted all over the building via airflow ducts.

Not all unrelated health issues are caused by poorly maintained air-con systems. Indeed, a well-designed air-conditioning system installed and maintained by a reputable company like us can actually boost the health of your building!

Here at Askews, we have over two decades of experience in heating, cooling and ventilation services. Click here for a free quote, or give us a call on 01282 863 825.

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