Oct 2, 2015



Legionnaires’ disease is normally contracted by inhaling small droplets of water (aerosols), suspended in the air, containing the bacteria.

What is Legionnaires’ disease?
Legionnaires’ disease is normally contracted by inhaling small droplets of water (aerosols), suspended in the air, containing the bacteria. Certain conditions increase the risk from legionella when:

a. the water temperature in all or some parts of the system may be between 20–45 °C, which is suitable for growth;
b. it is possible for water droplets to be produced and if so, they can be dispersed;
c. water is stored and/or re-circulated;
d. There are deposits that can support bacterial growth, such as rust, sludge, scale, organic matter and biofilms.

Legislation applicable to the control of legionella

  • Health and Safety at Work etc Act 1974
  • Control of Substances Hazardous to Health Regulations 2002
  • The Management of Health and Safety at Work (Amendment) Regulations 2006
  • The Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013
  • The Safety Representatives and Safety Committees Regulations 1977
  • Health and Safety (Consultation with Employees) Regulations 19966

Legal duties of duty holder
To comply with legal duties, duty holders should:

a. Identify and assess sources of risk. This includes checking whether conditions will encourage bacteria to multiply. For example, if the water temperature is between 20–45 °C, if there is a means of creating and disseminating breathable droplets, such as the aerosol created, e.g. by cooling towers, showers and spa pools; and if there are ‘at risk’ susceptible people who may be exposed to the contaminated aerosols
b. if appropriate, prepare a written scheme for preventing or controlling the risk
c. Implement, manage and monitor precautions – if control measures are to remain effective, regular monitoring of the systems and control measures is essential. Monitoring general bacterial numbers can indicate whether you are achieving microbiological control and sampling for legionella is another means of checking that a system is under control;
d. keep records of the precautions
e. appoint a competent person with sufficient authority and knowledge of the installation to help take the measures needed to comply with the law
Most businesses will appoint an external company to carry out a Legionnaires’ risk assessment and be the named competent person ensuring the above points are covered.

Risk assessments
There are several risk factors that that the duty holder must assess and review. Section 41 of the ACOP states:

There are a number of factors that create a risk of someone acquiring legionellosis, such as:
a. the presence of legionella bacteria;
b. conditions suitable for growth of the organisms, e.g. suitable water temperature (20°C–45°C) and deposits that are a source of nutrients for the organism, such as sludge, scale, rust, algae, other organic matter and biofilms;
c. a means of creating and spreading breathable droplets, e.g. the aerosol generated by cooling towers, showers or spa pools;
d. the presence (and numbers) of people who may be exposed, especially in premises where occupants are particularly vulnerable, e.g. healthcare, residential and nursing homes.

Risk assessment
The duty holder must ensure that a risk assessment is undertaken. The risk assessment can be done by an external specialist. The duty holder is the person who is either the employer, self-employer or the person in control of the premises. Section 28 of the ACOP states that a suitable and sufficient assessment must be carried out to identify and assess the risk of exposure to legionella bacteria from work activities and water systems on the premises and any precautionary measures needed.

Have you carried out a risk assessment on your premises?

Principal Hygiene have a team of Legionella Risk assessment professionals call us for a quote or for some easy to follow advice…….Call Mary on 01772 817600 or email her at mary@principalhygiene.co.uk.

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