Legionella risks in your workplace

When water systems can be at risk

Any water system, with the right environmental conditions, could be a source for legionella bacteria growth. There is a reasonably foreseeable legionella risk if your water system:

• has a water temperature between 20–45°C
• creates and/or spreads breathable droplets, for example aerosol created by a cooling tower, or water outlets
• stores and/or recirculates water
• is likely to contain a source of nutrients for the organism to grow, such as rust, sludge, scale, organic matter and biofilms

Most common sources of legionella

The most common sources of legionella are in man-made water systems including:

• cooling tower and evaporative condensers
• hot and cold water systems
• spa pools

There are also a number of other systems that can create a risk of legionella, such as humidifiers, air washers, emergency showers, or indoor ornamental fountains.

Your legal duties

If you are an employer, or someone in control of premises (such as a landlord), you have a duty to understand and manage legionella risks.

All systems require a risk assessment but not all systems will require elaborate control measures. A simple risk assessment may show the risks are low and being properly managed to comply with the law.

In such cases, your assessment may be complete and you may not need to take any further action, but it is important to review your assessment regularly in case anything changes in your system.

Further information is available in Legionnaires’ disease: what you must do.