The obligation
Duty holders must conduct regular microbiological sampling for Legionella and total counts, and must not treat a single result as conclusive — a program of monitoring is required.
The Code sets minimum microbiological monitoring requirements: monthly total count sampling and quarterly Legionella sampling for cooling towers. Results must be interpreted within the context of the ongoing monitoring program — a single positive result is not conclusive but triggers investigation and corrective action. Action levels are specified for Legionella concentrations, with escalating responses including immediate remediation and notification. Records of all results must be kept.
- What
- Duty holders must conduct regular microbiological sampling for Legionella and total counts, and must not treat a single result as conclusive — a program of monitoring is required.
- Source
- worksafe.wa.gov.au
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Labels
monitoring
microbiological
Legionella sampling
action levels
Official sources
Frequently asked questions
Which WHS law does this come from?
Microbiological Monitoring and Interpretation of Results is a WHS requirement set out in Prevention and control of legionnaires disease (WA). It is made under Work Health and Safety Act 2020 (WA). The relevant provision is Prevention and Control of Legionnaires Disease > Monitoring.
What does this WHS obligation require?
Microbiological Monitoring and Interpretation of Results is a WHS obligation under Prevention and control of legionnaires disease (WA). In short, Duty holders must conduct regular microbiological sampling for Legionella and total counts, and must not treat a single result as conclusive — a program of monitoring is required.
What changed recently?
Microbiological Monitoring and Interpretation of Results was last updated on 31 July 2026.
