How long is a Legionella Risk Assessment valid?

If you search the Internet you will find lots of different answers to this question quoting different time periods.  This may lead you to suspect some must be wrong.  However, to a degree they are probably all correct but there is actually no specific or defined validity period.  The important thing is to understand the legal background to a Legionella Risk Assessment and then you can understand how the validity will depend upon the exact details of your situation.

In the UK, a Legionella Risk Assessment is a special kind of Risk Assessment known as a COSHH Assessment.  COSHH stands for the Control of Substances Hazardous to Health.  The current rules are published in the Control of Substances Hazardous to Health (COSHH) Regulations 2002.  You can find out more in the Health & Safety Executive (HSE) publication INDG136 – Working with substances
hazardous to health.

The regulations require that a COSHH Assessment should be revisited regularly to ensure that it is kept up to date.  It is also the duty of the responsible person to determine the date of the first review and the length of time between successive reviews as part of the assessment process.  Both of these periods will depend on type of risk, the work, and the responsible person’s judgement on the likelihood of changes occurring.

The law requires that a COSHH assessment, including Legionella Risk Assessments, be reviewed immediately if:

  • There is any reason to suppose that the original assessment is no longer valid, e.g. evidence from the results of examining and testing engineering controls, reports from supervisors about defects in control systems; or
  • Any of the circumstances of the work should change significantly and especially one which may have affected people’s exposure to a hazardous substance

The HSE point out that the requirement is for a review of the assessment.  This does not mean that the whole assessment process will have to be repeated at each review.  The first purpose of review is to see if the existing assessment is still suitable and sufficient.  If it is, then you do not need to do any more.

Even if it appears that the assessment is no longer valid, it does not mean that the whole assessment has to be revised.  Only those parts that do not reflect the new situation need amending.

Whether or not there is any real change in the situation, there is an absolute requirement to review the situation on a regular basis.  Without this, there is a danger that gradual change over a period of time goes unnoticed and the assessment becomes unsuitable and insufficient by default.  It is generally accepted that this period should not exceed 12 months but may need to be shorter if there are high risks and can be extended if there is a stable situation and the risks identified are very low.

It should be noted that any Legionella Risk Assessment in place should be immediately reviewed if any of the following apply:

  • There are any changes to the water system or its use.  This can include the installation of new taps, boilers and the like.
  • There are changes to the use of the building in which the water system is installed.  For example, a dwelling may become an House of Multiple Occupation.  Alternatively, a rented property may be empty and out of use for a period of time.
  • There is availability of new information about risks or control measures.  This can include new guidance for specialist items like cooling towers, air conditioning systems, spa pools etc.
  • The results of checks indicate that control measures are no longer effective or there is a case of legionnaires’ disease / legionellosis associated with the system.  This could include visible algae growth, unpleasant smells, discolouration of the water or a build up of sludge in pipes or water tanks.
  • There are changes to key personnel.  This would include a change in the tenants.  New tenants will need to be informed of appropriate control measures they should and may be at higher or lower risk.  Their occupancy may also follow different patterns which can change the risks from Legionella in the building.
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