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HSG 274 updated for 2024

The Health and Safety executive (HSE has released an update to HSG 274 Part 1 The control of Legionella bacteria in evaporative cooling systems (cooling towers and evaporating condensers).

Part 1 of HSG274 now has amended guidelines for:
  • DPD No 1 testing methodology
  • cooling water pH

The two are inter-related. DPD (diethyl-p-phenylenediamine) testing is used to measure the free chlorine and bromine in biocides that kill bacteria, and is used to determine dosing levels, but raised cooling water pH levels can reduce the efficacy of these halogen-based biocides. So, pH levels should be used to determine the correct dosing to prevent the growth of Legionella.

Is your biocide dosing pH corrected? As a duty holder you should now check with your own team and/or your water hygiene specialist to make sure that your systems are properly under control.

Down load the HSG guidance free here.

What is a duty holder?

HSG274 guidance is for duty holders, which includes employers, those in control of premises and those with health and safety responsibilities for others, to help them comply with their legal duties. These duties include identifying and assessing the source of risk; preparing a scheme to prevent or control risk; implementing, managing and monitoring precautions; keeping records of precautions; and appointing a manager responsible for others.

Parts 2 and 3 of HSG274 offering guidance on the control of legionella in hot and cold water systems and other risk systems remain unchanged.

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