Evaporative cooling systems and Legionnaires' Disease

One of the questions we frequently get asked is whether you can catch Legionnaires’ disease from evaporative coolers. 

We are happy to report that there have been no recorded cases of a portable evaporative cooler causing Legionnaires’ disease and research indicates transmission of the bacteria is not possible by the evaporative method.

What is Legionnaires’ disease?

It is a very serious type of pneumonia caused by breathing in small droplets of water that contain bacteria called Legionella.  Legionella bacteria are found naturally in moist environments such as lakes and rivers, and other water sources. The bacteria causing Legionnaires disease are very common, but only build up to dangerous concentrations in -

·         Warm, stagnant water - evaporative cooling fans operate from a supply of cold fresh water, so the bacterium doesn’t have the opportunity to multiply.

·         Limescale and slime – regular cleaning of wet surfaces with a mild bleach solution, will prevent a build up forming.

How is Legionella bacteria transmitted?

Infection is mainly through inhalation of contaminated aerosols which must be large enough to hold the bacteria (between one and five microns in size). To contract Legionnaires’ disease, a person has to inhale the contaminated particles deeply into the lungs and they must be susceptible to it.

Can evaporative coolers transmit the disease?

Properly maintained portable evaporative coolers will not transmit the disease because they produce no aerosols, so even if bacteria were present in the mobile cooling unit, there is still no mechanism there to transfer them to humans.  Room evaporative air coolers should not be confused with cooling towers or evaporative condensers, which involve different technology.

In order to cool, mobile evaporative coolers cool air close to its wet bulb temperature.  The water temperature has to be below the air temperature, and so water very rarely rises above 20°C which is outside the range in which the Legionella bacteria would grow (between 20-45 °C) 

Maintenance and servicing of evaporative coolers

The portable evaporative coolers supplied by London Cool for either hire or sale are serviced by our engineers who carry out a thorough service which includes ensuring that all water is drained from the mobile unit.    

The engineers will clean the coils and pipework in the cooling unit to ensure no stagnant water, limescale or slime is present, all potential breeding grounds for the legionella bacteria.  We do not recommend the use of water additives as these could cause allergic reactions.

All wet surfaces of the fan and casing are cleaned with a specialist solution before rinsing and drying. The serviced unit is then run to ensure optimum efficiency in operation.

When not in use for long periods, water should be drained from the unit so there is no standing water to rise to ambient temperature.   Conversely, when a mobile evaporative cooler has been in use for more than 6 months then it is recommended the unit is cleaned, or serviced by our engineers, to ensure it is working at maximum efficiency. 

 Mobile evaporative air coolers are an environmentally-friendly and cost effective way of cooling.  They are an excellent choice in areas where there is no convenient way of ducting out the hot air produced by other types of portable air conditioner.  The portable coolers provide the basic moisture that the human body needs as well as removing static electricity from very dry areas.  They also remove unhealthy pollutants from the indoor atmosphere and can help in reducing the effects of asthma or similar conditions.

This type of cooler is often seen on station platforms, in airports, retail units or warehousing where there are no windows, in open offices or for outdoor or marquee cooling for events.

To find out more about our range of mobile evaporative coolers from manufacturers such as Honeywell, Munters, Jetstream, Antartico, Portacool, Seeley, Convair or Sumo, do give us a call on 0800 440 444 or visit our website www.londoncool.com for more information.