An in-depth look at Legionella


Legionella is a type of bacteria that causes diseases like Pontiac and Lochgoilhead fever and, worst case, Legionnaire’s disease.

Legionnaire’s disease

Legionnaire’s disease is a severe form of pneumonia and can be deadly. In 2017 alone, 693 cases of Legionnaire’s disease were reported/notified – a 40% increase on 2016’s figure.

When it comes to Legionnaire’s disease, everyone’s susceptible. That said though, individuals who fall into any of the below categories may be at greater risk of contracting it:

  • People who’re 45-year-old or above;
  • Smokers and heavy drinkers;
  • Individuals with diabetes, lung and heart disease;
  • People suffering from chronic respiratory or kidney disease; or
  • Anyone who has an impaired immune system.

Where does Legionnaire’s disease exist?

Natural water supplies – like rivers, lakes, reservoirs and ponds – host large quantities of the bacteria Legionella. Due to the conditions though, this isn’t where people tend to contract it.

More commonly, Legionnaire’s disease is apparent in places like cooling towers, spa pools, hydrotherapy baths and hot and cold water systems – to name just a few, where temperatures are high enough to support bacteria growth and the network is insufficiently managed.

The optimum temperature for Legionella growth and multiplication is between 20-45°C – with the provision of nutrients, like rust, sludge, scale and biofilms. Anything lower than 20°C is too cool for the bacteria to activate, and anything above 60°C is too hot for it to survive.

How is Legionnaire’s disease caught?

Legionnaire’s disease is caught by simply breathing in small droplets of water that contain Legionella particles.

Employees, visitors, customers, clients and anyone else in your premises run the risk of being exposed to contaminated water, and so it’s essential you have appropriate measures in place.

Your responsibilities

As an employer, it’s your responsibility to control any risks associated with Legionella exposure. To meet these, there’s a five-step process to follow – we’ll delve into each of these now.

1. Identifying and assessing risks

A competent person must carry out a thorough risk assessment to assess whether any of your water systems are likely to pose a Legionella hazard.

During the risk assessment, you should look out for things like:

  • Does the water temperature sit between 20-45°C in any parts of the water system(s)?
  • Is water stored and/or re-circulated in the system?
  • Are nutrients around for the bacteria to feed off?
  • Are any employees, visitors, residents, etc. at greater risk due to their age, habits or health condition?

For an in-depth look at how to perform a proper risk assessment, check out our free guide on it here.

2. Manage the identified risks

Once risks have been identified, it’s time to manage them. Prioritise the risks in terms of how harmful they could be, and consider who will be affected – remember, it’s not just employees and residents; visitors, customers, inspectors and suppliers, for example, could be impacted too.

3. Prevent or control the risk

Your first port of call should be preventing any Legionella risks. For example, if you’re currently using a wet cooling tower which is producing Legionella-infected water droplets, could you switch to a dry air-cooled system?

Essentially, the aim of this exercise is to ensure all your water systems operate in a way that isn’t conducive to the growth and spreading of Legionella.

In the event that you identify a risk that can’t be prevented, you must put appropriate measures in place to control the risk as best you can – if you need a hand working out what these are, get in touch with our Health & Safety experts.

4. Accurate records

If you’ve got five or more employees on your books, you’re legally required to keep a written record of your risk assessment. Your records should include information like:

  • The name on the individual who conducted the risk assessment;
  • Any significant findings uncovered during the assessment;
  • What measures have been put in place to prevent or control the risks;
  • An overview of the condition of your water systems; and
  • The results of any water system inspections, tests or checks.

Although this isn’t a legal requirement if you have fewer than five employees, it’s still good practice to keep a written record for future reference.

The management process of assessing and continually monitoring your water functions should be completed by a competent person – this could be in the form of a third party specialist.

5. Other duties

In addition to steps one to four, there are a couple of other responsibilities to be aware of:

Notification of Cooling Towers and Evaporative Condensers Regulations 1992: if you have a cooling tower or evaporative condenser on your site, you must let your local authority know where it’s situated.

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations: if you’ve an employee who’s been working on cooling towers and/or hot and cold water systems and you suspect they may have contracted Legionella, you must report it.

How to prevent Legionnaire’s disease

The easiest way to prevent Legionnaire’s disease is by implementing measures that allow you to appropriately regulate your water temperature.

As we touched on earlier, the optimum temperature for Legionnaire’s growth is between 20-45°C. With this in mind, you should ensure:

  • Hot water contained in hot water cylinders is at least 60°C;
  • Hot water’s distributed at a minimum of 50°C; and
  • Cold water’s stored and distributed below 20°C.

A nominated competent person should be in charge of regularly monitoring your water temperature, and thoroughly inspecting and cleaning your systems.

We’re here to lend a hand

When it comes to Legionella, there can be a lot to get your head around – which is where we come in.

With everything from choosing your competent person and conducting risk assessments, to the management and monitoring of hazards, our Health & Safety experts are here to lend a hand and remove the hassle.

Get in touch with the team on 0345 844 1111 or to see how we can help.

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