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In recent weeks we have seen an increase in legionella related issues.  We urge you to ensure that you have sufficient control measures in place to mitigate the build-up of the legionella bacteria within your water systems.  Systems that are lay dormant during lockdown, particularly with the current weather conditions are vulnerable and could be harbouring low levels of bacteria that may breed to potentially harmful levels.

Employers, the self-employed and people in control of premises, such as landlords, have a duty to protect people by identifying and controlling risks associated with legionella. 
If your building was closed or has reduced occupancy during the coronavirus (COVID-19) outbreak, water system stagnation can occur due to lack of use, increasing 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, 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 HSE’s guidance What is Legionnaires’ disease?.

Hot and cold water systems
If hot and cold water outlets are used infrequently, flush them at least once a week to prevent water stagnation. If you cannot do this, work with your competent person to ensure systems are cleaned and, if required disinfected before the building is occupied.
For further guidance read:

Temperature control is the main form of control used in hot and cold water systems. It is generally accepted that the cold system should not exceed 20°C and the hot supply should exceed 60°C. If you can, check these at least once a month to ensure suitable temperatures are being achieved.  Should you require further information then we would be happy to assist in advising how these temperatures are taken .

Air conditioning units
If your workplace has been closed for an extended period and has air conditioning units that have a source of water that can generate aerosol, you will need to assess the risks of legionella being present within them before restarting.
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.  
When you review your risk assessment, decide what the risks are for your units and if you need to clean them safely, before they are turned on.

Personal protective equipment (PPE) required for cleaning water systems
If you need to clean water systems, it’s likely that respiratory protective equipment (RPE) will be needed. 
RPE must: 

  • be adequate
  • be suitable
  • provide an assigned protection factor of at least 20 

Disposable RPE, such as FFP3 respirators used by health and care workers, may be in short supply. If your usual types of RPE are unavailable, you can source alternatives as long as your risk assessment demonstrates they are suitable and adequate for workers and the task. 
An alternative could be: 

  • a reusable half-mask or full-face respirator fitted with a P3 filter
  • a powered respirator and hood class TH2 or 3
  • a powered respirator and close-fitting full-face mask class TM3
  • an air-fed hood or full-face mask supplied with breathing quality air 

You can find more information in our guide Respiratory protective equipment at work (HSG53) (PDF)- Portable Document Format .

Getting specialist help
Call us on 01462 892 021 for advice or assistance with any matter and we will be delighted to assist you.
Alternatively, you can email us at 

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