Legionnaires Disease

Fines totalling £80,000 were paid out by the hotel, the MD of an engineering company and a health and safety consultant advising them.

The disease was attributed to a 'humidifier' installed to spray a mist over buffet food to keep it looking fresh. However, the unit was installed incorrectly, water filters that treat the water before it is sprayed were missing as well as an automatic drain valve.

As a result, untreated water was sprayed over the food and was also left to stagnate in the unit when not in use allowing the Legionella bacteria to develop.

What is Legionnaires Disease?

Legionnaire's disease is a pneumonia-like illness that has often proved fatal and has a typical incubation period of between two and ten days. Outbreaks can be caused by failure to keep water systems clean and free of the Legionella bacteria. The bacteria can survive in a water temperature between 6 – 60ºC and remain dormant at lower temperatures with favourable growth temperatures ranging between 20 – 45ºC. If the conditions in the water system are favourable, the bacteria can multiply and spray or droplets produced by the system can be inhaled with fatal consequences.

Assessing the risk from Legionella

Legionella bacteria fall within the definition of a 'substance hazardous to health' and, as such, the provision of the Control of Substances Hazardous to Health Regulations 2002 apply, including the assessment of risks and application of suitable control measures.

A risk assessment should be undertaken by the person having control of the system, which may be the owner or manager of the building or equipment.

The assessment process should consider:

• How Legionella may enter the system, including the source of the water supply.
• Whether the temperature range is favourable for growth.
• Whether materials in the system are likely to harbour or promote growth. and
• The likelihood of droplet or spray formation both under normal or fault conditions.

Once a significant risk has been identified, then a written scheme of control should be developed which fully documents the precautions that need to be taken. The written scheme would include:
• Operating parameters of the system.
• Control measures necessary to control the risk.
• Monitoring arrangements.
• Cleaning and disinfection procedures.
• Commissioning, decommissioning, shut down and start up procedures.
• Monitoring arrangements for the system. and
• Maintenance requirements.

As with all risk assessments they should be reviewed regularly and when any changes are made to the system or equipment.

Suitable and sufficient records must be kept for at least a period of two years and signed by the person carrying out the task.

Systems at risk from Legionella (Source HSE)

Spray humidifiers – these should be cleaned and disinfected including make-up tanks and all wetted surfaces, de-scaling as necessary at least 6 monthly.
Confirm the operation of non-chemical water treatment (if present) at least weekly.

What do I need to do?

If in any doubt about the risks from the systems you have installed contact the supplier of the equipment and ensure that the installation, operation, maintenance and cleaning routines are suitable and sufficient.

Ensure that you have a written risk assessment and that staff are aware of and understand the risk and the control measures necessary and that staff involved in the cleaning and maintenance of the systems have suitable understanding and training to carry out the task.