(852) 5923 7263Request a quote
Legionella control is not a product, it is a programme: assess the risk, remove the conditions the bacteria need, dose chemistry that actually works at your operating pH, test to confirm, and document all of it. Below 10 cfu/mL counts as “undetected” under the EMSD Code of Practice. At or above 1,000 cfu/mL you receive a statutory nuisance notice requiring emergency decontamination. Our job is to keep you comfortably in the first range and able to prove it.
Legionella is the bacteria behind Legionnaires' disease, a serious pneumonia contracted by inhaling contaminated aerosol. It lives naturally in water at harmless levels; the danger comes when a building system amplifies it and then throws it into the air. Cooling towers do both, which is why they are regulated.
The control problem is more subtle than “add biocide”. Legionella shelters inside biofilm and replicates within amoebae that live there, which means chemistry that looks adequate on paper may never reach it. Control is therefore always a combination of cleaning, chemistry and verification — never one of the three alone.
Since 2011 the EMSD can enter premises and sample fresh water cooling towers at random. You do not get to choose the day you are tested, which means the only workable strategy is to be in range every day. See Legionella in water systems for the full picture.
This is the one risk on the site that is not primarily financial. A Legionella outbreak is a public health event with people at the centre of it, and the costs that follow — statutory, legal, reputational — are secondary to that. Financially it is also the least predictable: an ordinary NPV model handles a slow energy bleed well and a catastrophic tail badly. That is a limitation of the model, not evidence of safety, and it is why this risk is managed rather than calculated.
Below 10 cfu/mL is treated as “undetected” under the EMSD Code of Practice for Fresh Water Cooling Towers. At or above 1,000 cfu/mL a statutory nuisance notice requires emergency decontamination and re-testing — see Legionella in water systems for the Hong Kong numbers in full.
Most often biofilm, or pH. Biofilm physically shelters the organism from chemistry that is present and working elsewhere in the system. And chlorine loses most of its efficacy as pH rises — at pH 9 roughly 95% is in the weak form. The residual reads fine; the kill is absent.
Yes. Legionella is invisible, and a treatment programme without verification is an assertion. Testing is also what gives you a defensible record if anyone asks how the system was managed.
We will assess the risk, sample the system, and build a programme that keeps you in range.