The Health and Safety Executive (HSE) has issued advice to employers about the potential of increased legionella risk due to COVID-19.
- With buildings closed, water systems may have become stagnated, creating ideal conditions in which legionella can thrive, and
- With the easing of restrictions and workplaces reopening, there are likely to be larger groups of people exposed to this potential risk.
Why is there an Increased Legionella Risk?
One of the conditions in which legionella thrives is stagnant water in purpose-built water systems.
With so many buildings being closed during the pandemic, or open only intermittently, the risk is that they have more stagnant water in their systems than is normal.
Stagnant water is water that has little or no movement, sitting in the same place for long periods.
Normally, buildings will have water supplies that are in pretty much constant use – drinking, washing, air conditioning. Once these supplies are no longer in consistent use, the water in them can become stagnant, which is when bacteria start to multiply.
Water that is constantly moving flushes through the system. Stagnant water does not, giving bacteria such as legionella the time to grow and spread.
What is the Government’s Advice?
If you have had to close your building during the pandemic, or it has had fewer people occupying it during this time, then there could be an increased risk of legionella in stagnant water.
Therefore, you should review your risk assessment and manage the legionella risk.
You should do this BEFORE you start using your water system again. If you use larger air conditioning units, these may also present a risk. Determine the level of risk and if you need to clean these units before switching them on.
If there are commercial spa pools or hot tubs on your premises that are not in use, you should drain, clean and disinfect them.
Recommended Methods of Legionella Control
HSE recommends temperature control as the main means of managing legionella risk.
Legionella grows in water at temperatures of 20–45°C. Colder than 20°C and legionella goes dormant, hotter than 50°C and it starts to die.
You can also apply a water treatment, using a certified disinfectant as a biocide to kill off and prevent legionella growth.
Who’s Most at Risk from Legionella?
You can develop legionnaires’ disease from breathing in airborne legionella bacteria.
Legionnaire’s disease is a disease of the lungs, and it can affect anyone exposed to legionella, and if left untreated, it may prove fatal.
Certain groups are more at risk. These are:
- People aged 45 and over
- People with pre-existing conditions such as respiratory illnesses, cancer or kidney diseases.
- People with weak or deficient immune systems
- Smokers and heavy drinkers.