Can evaporative cooling cause Legionella?

January 16, 2019

There have been a spate of cases recently of councils and other organisations being fined for allowing Legionella to develop in their buildings, and on the back of this we thought it was worth publishing information about whether Legionella could be caused by evaporative cooling.

The simple answer to this is that it could in theory – however our evaporative cooling systems are designed specifically to comply with HSE technical guidance on Legionnaires. So, if we install it and you have it serviced and maintained properly, then you have nothing to worry about. This is because your system will not be producing the water droplets that cause Legionella, but we explain more below.

What is Legionella and how do you catch it?

Legionnaires’ disease is a form of pneumonia. It is contracted by breathing in very small droplets of water contaminated by legionella bacteria. It’s uncommon but can be very serious – even fatal. Outbreaks of the illness occur from exposure to legionella growing in systems where water is maintained at a temperature high enough to encourage growth.

When could Legionnaires be caught from an evaporative cooling system?

According to the HSE there is a reasonably foreseeable legionella risk in your water system if:

  • Water is stored or re-circulated as part of your system;
  • The water temperature in all or some part of the system may be between 20–45 °C;
  • There are deposits that can support bacterial growth, such as rust, sludge, scale and organic matter.
  • It is possible for water droplets to be produced and, if so, whether they can be dispersed;
  • It is likely that any of your employees, contractors, visitors etc could be exposed to any contaminated water droplets.

How do the evaporative coolers we use guard against Legionella?

  • Avoidance of stagnant water – The coolers automatically drain when not in use
  • Low water operating temperature – The temperature of the water very rarely goes above 20°C even when the temperature is very hot outside. Below is a temperature sampling of an Evaporative cooler in the UK, and it can be seen that the water temperature hardly ever exceeds 20°C

  • Avoidance of deposits supporting bacterial growth –
    • All wetted surfaces, except for the pads, are plastic and so do not degrade to create nutrients that could feed bacteria growth.
    • The pads are treated to stop rotting
    • During operation the cooler is regularly drained and flushed to remove particles which have been filtered out of the air
    • A salinity control system prevents scale formation. Scale breakdown could provide nutrition and so this is avoided.
  • There is also the option of using bromine as a biocide
  • Droplets can’t be formed – A wetted media evaporative cooler does not create droplets provided the air velocity over the pads does not exceed a set limit. For the pads we use this is 3m/s. The EcoCooler evaporative cooling systems we install have a maximum velocity of 1.7m/s
  • Maintenance – Provided the units are maintained by qualified personnel such as the team at Vent-Tech, regular servicing will ensure that your evaporative cooling system continues to function properly and there is no risk to your team.

A 100% safety record.

There have been no instances of Legionella recorded from the evaporative cooling units we have installed – or indeed for any EcoCooling evaporative cooling units installed (the brand we fit).

As we said at the beginning, provided your Evaporative cooling system is designed to comply with HSE guidance, and is installed and maintained by a reputable company such as ourselves, then you have nothing to worry about.
If you would like to discuss whether evaporative cooling could be the cooling solution you require for your building, please pick up the phone to us on 0117 964 7945 or send us an email.