Stakeholder - ALS Environmental

Changes in Legionella reporting

Following on from the HSG 274 guidance about Legionella, the United Kingdom Accreditation Service (UKAS) have issued a technical bulletin regarding the reporting of all Legionella results. To help our customers comply with industry standard, ALS have taken the necessary steps to ensure our processes are in line with this standard in order to provide you, our customer, with accurate and reliable data.

UKAS Guidance

Key paragraphs from the UKAS guidance, affecting the way in which the results are reported, are included below:

Report the confirmed presence (or absence) of Legionella pneumophila and the presumptive presence (or absence) of other Legionella species. Report absence as “not detected” in the volume examined. Ideally report the serogroup of all isolates of Legionella pneumophila.

To read the HSG 274 bulletin, please click here

Changes for our customers

The impact of this change is that where less than 1 litre of sample is received, laboratories will not be able to claim accreditation for a Positive Legionella result that is expressed as cfu/litre as UKAS have clearly stated in the guidance.

ALS will be providing customers with a 1 litre Legionella sample bottle as opposed to the current 500ml bottle. It is adequate to use 2x500ml bottles where you have sufficient stock of 500ml bottles but they must be taped together so that it is clear to ALS that on submission to the laboratory that they are the same sample from the same sampling point.

ALS have already amended the ALS Legionella test report such that for samples Not Detected (ND) for Legionella bacteria, the results are now expressed as “ND cfu in volume” as the accredited results. The volume analysed will be present on the test report as currently displayed but the volume will now be expressed in millilitres “ml” not grams “g”.

If 1 litre of sample is analysed, the result expressed as “cfu in volume” is the same as a result expressed as cfu/L.

If less than 1 litre of sample is analysed, an additional results box will appear on your certificate of analysis showing calculated results expressed as “cfu/L” for ease of reference to published action levels.

These calculated results will not be accredited.

It is imperative that all sample bottles should be filled fully as ALS will be measuring the volume content of the sample bottle. Any volume that is less than 1000ml (1 litre) would mean that in the event that the sample is positive, the result in units of “cfu in volume” will be accredited but the calculated result in units of “cfu/L” will not be, as specified by UKAS.

Additionally for positive Legionella results, the ALS report will include the total Legionella bacteria present. (which is a sum of all Legionella species provided on the report.)

Legionella testing by ALS

ALS are market leaders in Legionella analysis and we offer this type of analysis by two methods. We have detection by Standard Culture via MALDI-ToF instant confirmation and Enumeration of Legionella by Rapid Detection, using a method based on the Polymerase Chain Reaction (PCR). Both of these methods can be used for the identification of Legionella and Legionella pneumophila species, with the MALDI-ToF providing a full Legionella speciation. The library of species we have at ALS is second to none.

MALDI-ToF technology not only provides you with instant confirmation of Legionella but also removes the need for the industry-normal 2 day confirmation process for presumptive positive samples.

For more about ALS Environmental’s Legionella analysis and MALDI-ToF confirmation, or for guidance regarding these changes, please feel free to contact us. For further technical assistance contact our technical experts, or call the team on 02476 421 213.


Contact Us

ALS Environmental

Torrington Avenue



T:  024 7642 1213

or :

Units 7 & 8

Hawarden Business Park

Manor Road








We had potential water quality problem due to the actions of a third party and needed samples taken as a matter of urgency. Although this was outside the strict terms of our contract with ALS they were able to provide a sampler on a Friday afternoon, get the samples taken and returned to their labs for analysis.

They backed this excellent performance up by emailing us the sample results over the weekend. All in all a great piece of customer service!

Bob Windmill, Head of Water Quality, Independent Water Networks

ALS are a really easy company to deal with their professional attitude to the range of services they provide for us is second to none. The people there listen carefully and respond very quickly to our requests , we have dealt with them for the last eight years and their customer advisors understand our business and not only their own.”

Ken Begg, Director, Aberdeen Sampling Ltd
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