A definitive guide to safeguard against legionella in the workplace

08 December 2020

Woman in yellow top drinking a hot drink in front of a water filter and coffee machine
A definitive guide to safeguard against legionella in the workplace

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As we experience a second national lockdown, many organisations will be facing a variety of long-term problems. For those that are office-based, one of these could include legionella in the workplace (legionnaires disease), which will be more likely to occur whilst buildings are closed and unattended during the lockdown.

This potential obstacle can have a detrimental effect to your employees’ health and your brand’s image which makes it a priority for you to safeguard against legionella in the workplace. In this article, we answer the key questions:

  • What is legionella?
  • What should be included in a legionella checklist?
  • What are the workplace laws surrounding legionnaires disease?

Before you investigate how to safeguard with your own legionella checklist, it is vital that you understand everything you need to know about the bacteria.

What is legionella?

Diseases caused by legionella bacteria are collectively known as legionellosis. The most serious of these is legionnaires disease which is a potentially fatal form of pneumonia that can affect anyone. Some factors put certain groups of people at greater risk than others, including:


People over 45 years of age are more at risk than younger people.


Smokers and heavy drinkers are more at risk from lung infections.


People suffering from chronic respiratory disease, kidney disease, diabetes, lung, or heart disease have a higher level of risk from lung infections.

Natural defences

Anyone with an impaired immune system has a higher risk of contracting legionnaires' disease.

Where can legionnaires bacteria be found?

The bacteria is most commonly found in natural water systems such as rivers and ponds. However, the conditions are not usually ideal for the bacteria to grow and people rarely become infected from these sources. Legionella often grows in purpose-built systems where water is maintained at a temperature high enough to encourage growth. These systems include:

Cooling towers

Cooling towers and evaporative cooling systems contain large amounts of water and are potential breeding grounds for legionella bacteria if they are not properly cleaned and maintained. Water within cooling towers is heated via heat exchange, which is an ideal environment for legionella bacteria to grow.

Dry/wet cooling systems

Sometimes referred to as hybrid or adiabatic coolers, these are designed to operate both in dry air-cooled mode and wet evaporative cooling mode. There are different types of dry/wet cooling systems, sometimes referred to as 'hybrid' or 'adiabatic' coolers, and these can have a wide range of risk profiles.

Hot and cold-water systems

Hot and cold-water systems, which can present a danger of exposure to legionella, can range in size, scale, and complexity. Some of the different types of systems are:

  • Smaller hot and cold-water systems
  • Non or low storage systems
  • Hot and cold-water storage gravity fed system
  • Pressurised mains-fed water system
  • Hot water storage only
  • Cold water storage only, mains pressure hot water system

Spa pools

Spa pool systems can be known by various names including hot spas, hot tubs, whirlpool spas and portable spas. If your workplace has one or more of these pools in a gym or spa, there is a reasonably foreseeable risk.

Other potential risks

There are a number of other risk systems that could potentially be a source for legionella bacteria growth. These include:

  • Humidifiers
  • Air washers
  • Emergency showers
  • Eye wash sprays
  • Indoor ornamental fountains
  • Aqueous tunnel washers etc

How does legionella spread?

Once legionella grows and multiplies in a building water system, this water containing the bacteria must then spread in droplets small enough for people to breathe into their system. These droplets are known as ‘aerosols’ from a contaminated water source.

Legionella can also affect people by being consumed via water that contains the virus. Although this is less common, this can happen when water accidentally gets into the lungs while drinking. Legionella is not spread from person to person but rather via the systems previously mentioned in the following conditions:


If your system has a water temperature between 20-45°C.

Water droplets

If your system creates and spreads breathable water droplets (known as aerosols) in a cooling tower, or other water outlet.

Stored water

If your system stores or re-circulates water.


If your system is likely to contain a source of nutrients for the organism to grow e.g. rust, sludge, scale, organic matter and biofilms.

What are the symptoms of legionnaires disease?

Legionnaires' disease typically develops 2-10 days after exposure to legionella bacteria. It often begins with the following signs and symptoms:

  • Headache
  • Muscle pain
  • Chills
  • Fever that may be 104 F (40 C) or higher

By the second or third day, you could develop other signs and symptoms that may include:

  • Cough, which may bring up blood and mucus
  • Shortness of breath
  • Chest pain
  • Gastrointestinal symptoms, such as nausea, vomiting and diarrhoea

These symptoms therefore highlight the importance to safeguard against legionella in the workplace. This brings us to our next key question.

What should be included in your legionella checklist?

If you are an employer, or someone in control of premises (e.g. landlord), you have a duty to understand and manage legionella risk management. You or the person responsible for managing risks, need to understand your water systems, the equipment, and its component parts. You can then identify whether they are likely to create a risk from exposure to legionella due to:

  • The water temperature in all or some parts of the system being between 20-45C
  • Water being stored or re-circulated as part of your system
  • Sources of nutrients such as rust, sludge, scale, organic matter and biofilms
  • Conditions likely to encourage bacteria to multiply
  • It being possible for water droplets to be produced

Check out our suggested legionella checklist.

Keeping records

If you have five or more employees, you must keep records. If you have less than five employees, you do not need to keep records although it is recommended to do so. Records should be kept for at least 2 years and should include details of:

  • Person or persons responsible for conducting the risk assessment, managing, and implementing the written scheme
  • Significant findings of the risk assessment
  • Written control scheme and details of its implementation
  • The state of operation of the system, i.e. in use/not in use
  • Any employees identified as being particularly at risk
  • Results of any monitoring inspection, test or check carried out, and the dates (and keep these for 5 years)

How do you ensure legal compliance surrounding legionella?

Control of Substances Hazardous to Health Regulations 2002 to 2015 (COSHH) provides an insight into this area. According to COSHH, hazardous substances are substances or mixtures of substances classified as hazardous to health under the EU CLP Regulations (EC) No 1272/2008. These can be identified by their hazard warning label and the supplier must provide a safety data sheet (SDS) for them.

Hazardous substances include:

  • Chemical and other substances used directly in work activities
  • Substances generated during work activities (e.g. diesel engine exhaust fume, welding by-products)
  • Naturally occurring substances (such as flour, stone, wood dust, animal fur and fungal spores)
  • Biological agents such as bacteria and other micro-organisms, including legionella in water systems

COSHH applies to virtually all substances hazardous to health except those that have their own regulations such as asbestos and lead, radioactive substances, those that have explosive or flammable properties.

You can discover all of the legal legislation you need to know with our EHS compliance software.

How can Ideagen assist you?

At Ideagen, we have software solutions that can assist you with creating a checklist to prepare your organisation to safeguard against legionella in the workplace and to ensure you are regulatory compliant on this issue.

Find out more about our software solutions.

Ideagen's James Vjestica
Written by

James Vjestica

As Ideagen’s Content Marketing Executive, James is primarily focussed on manufacturing and keeping individuals in this sector informed of the latest regulatory news and trends. He comes from a marketing background and is passionate about creating engaging content that answers questions relating to software solutions and regulatory changes.

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