Legionella analysis forms part of the legal duties under the Health and Safety at Work Act 1974 and must be conducted in accordance with the technical guidance set out in HSG274 – Approved Code of Practice for Legionella Control.
HSG274 clearly states:
“Samples should be tested by a laboratory accredited by UKAS to EN ISO/IEC 17025:2017. Analysis for legionella by culture should be carried out in accordance with BS EN ISO 11731:2017.”
In November 2025, UKAS issued a technical update concerning legionella testing methods used by laboratories. UKAS identified that some laboratories are omitting steps within the BS EN ISO 11731:2017 culture method. The omission of these steps can result in under recovery of legionella, directly undermining the reliability of results.
Although some laboratories had previously been listed as testing using methods based on BS EN ISO 11731:2017, UKAS has now formally reviewed this situation and stated:
“UKAS now takes the view that this deviation is too far removed from ISO 11731:2017.”
As a result, laboratories using such deviated methods can no longer claim accreditation for a method compliant with BS EN ISO 11731:2017 and are therefore not compliant with the requirements of HSG274.
Eurofins has always ensured that its legionella testing method is fully compliant with BS EN ISO 11731:2017, as we do not omit any steps from the standard method. While omitting steps may offer a financial advantage, it presents a serious risk of under-detection and therefore increases the potential for public health and safety failures. Eurofins is unwilling to accept these risks and remains committed to scientific integrity, public safety, and full regulatory compliance.
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January 2026
