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Legionella risks during the coronavirus outbreak

If your building has been closed, water system stagnation can occur due to lack of use. This increases the risks of Legionnaires’ disease.



Employers, self-employed and people in control of premises, such as landlords, have a duty to protect people by identifying and controlling the risks associated with legionella.

If your building has been closed or has operated at reduced occupancy during the coronavirus (COVID-19) outbreak, water system stagnation can occur due to lack of use. This increases the risks of Legionnaires’ disease.

You should review your risk assessment and manage the legionella risks when you:

  •  Reinstate a water system or start using it again
  • Restart some types of air conditioning units

If the water system is still used regularly, you should maintain the appropriate measures to prevent legionella growth.

You can find out what Legionnaires’ disease is, where it comes from, how people get it and symptoms and treatment by reading the following guidance from HSE – ‘What is Legionnaires’ disease?‘.

High risk areas

Hot and cold water systems

If hot and cold water outlets are being used infrequently, flush them at least weekly to prevent water stagnation. If you cannot do this, work with your competent person to ensure systems are cleaned (if required) before the building is occupied again.

For more information, read the full HSE guidance

Cooling towers and evaporate condensers

If you have cooling towers within your plant, you should already existing plans in place to ensure safe systems of work continue during any shutdown. This includes ensuring that:

  • Adequately trained personnel are available to carry out essential checks and monitoring
  • Chemical supplies are maintained appropriately

If cooling towers and evaporative condensers are likely to be out of operation for:

  • Up to a month – HSE recommend that you isolate fans, but circulate biocidally-treated water around the system for at least an hour each week
  • More than a month – HSE recommend that you drain down the systems and clean and disinfect them. Clean and disinfect the systems again before refilling and returning to operation

For more information, read the full HSE guidance.

Air conditioning units

If your workplace has air conditioning units that have a source of water that can generate aerosol and you have been closed for an extended period of time, you must assess the risks of legionella being present within them (before restarting them).

  • Small wall or ceiling-mounted units with closed cooling systems should not present a risk.
  • Larger units may present a risk if they have improperly drained condensate trays, or humidifier or evaporative cooling sections where water can stagnate, becoming a reservoir for bacteria to grow.

 Commercial spa pools and hot tubs

If commercial spa pools and hot tubs are:

  • Being used – You must maintain the existing control regimes
  • Not being used – You should drain, clean and disinfect them. You should also clean and disinfect them before returning them to use.

For more information, read the full HSE guidance.

Related Links

Read the full article on the HSE Website
– The Legionella Control Association has published guidance on managing water systems during the coronavirus outbreak.
– The Chartered Institute of Environmental Health has published guidance on legionella risks during the lockdown and reopening safely (PDF)

Getting Specialist Help

You may need advice from a competent person and/or specialist to help you identify and implement suitable controls for legionella.

The HSE recognises that getting specialist help may be difficult during the coronavirus outbreak. Whilst this is true, if you’re unable to appoint someone with the appropriate authority and competence to oversee the risk controls of water systems, you must consider stopping operation of the systems.

Get in contact

Compass HSC is a leading Lancashire based health and safety consultancy and we are ready to help. If you need any further clarity on managing Legionella risks,  or another matter relating to Safety and COVID-19, get in contact with the team.

Our team of health and safety consultants are available to discuss any concerns you may have. Contact us via email at or call us on 01253 735 755 or use the links below.

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Further information

For HSE’s latest news and advice on coronavirus visit:

For more specific guidance for your industry or sector visit:

Need some help?

Speak to one of our experts today

Book Online

Contact Compass HSC

A Lancashire based Health & Safety Consultancy

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