EMSD inspects fresh water cooling towers and publishes sampling results. Its January–August 2026 routine surveillance covered 533 samples from 321 buildings: 77 samples were at least 10 but below 1,000 cfu/mL, and 4 were at or above 1,000 cfu/mL. The table below links the published figures to their sources, checked on 16 September 2026.
The published results
These are the sampling announcements EMSD and the HKSAR Government have published, as cited on this site. Each row links to its source.
| Period | Samples | Buildings | ≥10 to <1,000 cfu/mL (advisory letters) | ≥1,000 cfu/mL (nuisance notices) | Source |
|---|---|---|---|---|---|
| December 2024 sampling round | 89 | 68 | Not stated in the announcement | 1 sample at or above the threshold | Government announcement, 8 Jan 2025 |
| January–August 2026 routine surveillance | 533 | 321 | 77 samples | 4 samples | EMSD sampling statistics (checked 16 Sep 2026) |
This is a dated snapshot checked on 16 September 2026, not a live feed. Check the linked EMSD source for subsequent updates.
How to read these numbers
Three things stand out for anyone responsible for a building:
- The sampling is real and ongoing. These are random surveillance visits — you do not get notice. Both selected periods include samples at or above the nuisance-notice threshold.
- Samples are not buildings. 77 of 533 routine samples (about 14.4%) were in the advisory band; another 4 reached the nuisance-notice threshold. Multiple samples may come from one building, so these percentages must not be presented as the share of buildings affected.
- The consequence at the top band is public. A tower at or above 1,000 cfu/mL draws a statutory nuisance notice requiring emergency decontamination and re-testing — and EMSD publishes the building locations issued with nuisance notices. The chemistry is recoverable; being on the list is a matter of public record.
What this means for a duty holder
Maintain treatment, monitoring, cleaning and records between inspections. Surveillance statistics describe tested samples; they do not predict the condition of an individual tower or replace its own water-quality monitoring.
Your own test results describe the samples taken at that time. Use them with inspection and maintenance records to assess control; they cannot guarantee the result of a future EMSD sample.
For the full rulebook — the thresholds, the action ladder and the record rules — see the EMSD Code of Practice explained. For what an owner is responsible for, see Legionella and cooling tower compliance. If a result has already come back high, or a notice has arrived, go straight to emergency Legionella and EMSD notice response; the printable checklist covers the routine duties for managing tower water quality.
Frequently asked questions
Does EMSD really sample Hong Kong cooling towers at random?
Yes. EMSD has carried out random cooling-tower inspections and water sampling since 2011 and publishes the results. Its January–August 2026 routine surveillance covered 533 samples across 321 buildings.
What is the difference between an EMSD advisory letter and a nuisance notice?
A result of at least 10 but below 1,000 cfu/mL draws an advisory letter putting the problem on record. A result at or above 1,000 cfu/mL draws a statutory nuisance notice requiring emergency decontamination and re-testing — failing to comply is an offence, and EMSD publishes the building locations issued with nuisance notices.
How many Hong Kong cooling towers fail EMSD sampling?
For January–August 2026, 77 of 533 routine samples were at least 10 but below 1,000 cfu/mL (about 14.4%); another 4 reached 1,000 cfu/mL or above. These figures were checked on 16 September 2026. Refer to EMSD for subsequent updates.
References
- HKSAR Government, EMSD announces latest sampling results for legionella at fresh water cooling towers, 8 January 2025 — the December 2024 sampling round.
- EMSD, Water Sampling of Fresh Water Cooling Towers — Statistics — regulatory actions by result band, and the routine surveillance figures for January–August 2026 (checked 16 September 2026).
- EMSD, Regulatory Control of Water Quality inside Cooling Towers — the advisory letter and nuisance notice procedure under the Public Health and Municipal Services Ordinance, Cap. 132.
- EMSD, Building locations of fresh water cooling towers detected with total legionella count ≥ 1,000 cfu/mL with nuisance notices issued (PDF, updated periodically).
Every job includes
- A free site visit and assessment
- A written quotation for your records
- A dated report after every visit
- Work that follows the EMSD Code of Practice
Would your towers pass a random sample?
We will test your water against the Code's criteria and tell you plainly where you stand.