Legionnaires’ Disease Prevention and Control Guide

Legionnaires’ disease risks should be controlled by preventing workers and others from inhaling contaminated water droplets, mist, dust or soil particles. For builders and tradies, the practical priorities are to identify potential sources, reduce aerosol and dust generation, maintain water systems and make sure specialist work is properly planned and recorded.

Information current: 7 August 2026.

Where can Legionella exposure occur?

Legionnaires’ disease is caused by Legionella bacteria. Exposure commonly occurs through inhaling contaminated aerosols from water systems or airborne particles from potting mix, mulch, compost and soil.

Construction, maintenance and property work may involve:

cooling towers and evaporative condensers
hot, cold and warm water services
showers, taps and infrequently used pipework
evaporative air conditioners and humidifiers
fountains, sprinklers, wash systems and water-based dust suppression
pressure cleaning and other spray-generating equipment
potting mix, landscaping soil, mulch and compost.

Legionella growth in water is encouraged by warm conditions, particularly between 20°C and 45°C, together with stagnation, low water turnover, biofilm, scale, sediment, sludge and corrosion products. Standby plant and systems left unused can therefore become important warning points.

What should be sorted before work starts?

The supervisor, contractor and person controlling the site should establish what systems or materials are involved and who is responsible for them. Review available design information, commissioning records, maintenance history, water-treatment records and manufacturer instructions.

Before starting, consider:

whether the task can generate mist, spray, droplets or airborne soil dust
whether water has been stagnant or equipment has been shut down
signs of leaks, slime, algae, scale, corrosion or poor drainage
whether workers, occupants or nearby members of the public could be exposed
how the system will be isolated, drained, flushed, cleaned or disinfected
whether chemicals are involved and current safety data sheets are available
whether competent water-treatment, hygiene or mechanical specialists are needed
what emergency, health escalation and incident-reporting arrangements apply.

Consult affected workers and coordinate with the builder, facility manager, building owner and specialist contractors. Controls should account for everyone who may be exposed, not just the person performing the maintenance.

What do good controls usually cover?

Effective control starts with suitable system design, followed by regular inspection, maintenance and monitoring. Water treatment and biocides may form part of the program, but they should support—not replace—clean systems, good flow, appropriate temperatures and sound housekeeping.

Depending on the system and task, controls may include:

eliminating unnecessary aerosol generation
shutting down or isolating equipment before inspection or cleaning
preventing stagnant water and flushing infrequently used outlets
keeping soil and potting products damp and handling bags carefully
using low-pressure watering methods to minimise dust and spray
cleaning, disinfecting and commissioning systems under an approved procedure
restricting access and protecting nearby occupants during hazardous work
selecting suitable gloves, eye protection and respiratory protection where residual exposure remains
using trained and experienced people for water treatment and specialist sampling.

For cooling towers, the Western Australian Code recommends a risk-based program incorporating at least monthly inspections, water treatment where applicable, microbiological monitoring and cleaning when necessary at intervals not exceeding six months. Site arrangements should follow current local requirements and the system’s assessed risks.

Testing is one part of verification. Legionella results should be interpreted alongside system inspection, operating conditions and treatment performance; an isolated negative result should not lead to reduced maintenance standards.

What documents and records are commonly needed?

A practical control system commonly includes a site risk assessment or JSA, plant operating and maintenance procedures, water-treatment arrangements, inspection schedules, test results, cleaning and disinfection records, chemical safety data sheets, contractor competency records, training records and an incident response process.

Check whether the work is high risk construction work under the applicable jurisdiction. If it is, the required SWMS must be prepared before that work starts and should address the actual task, site conditions and controls. Other activities may be managed through a site-specific risk assessment, JSA, permit, maintenance procedure or water-management plan.

Practical warning signs

Pause and review the work if there is unexplained spray, stagnant or discoloured water, slime, algae, heavy scale, blocked drains, damaged drift control, missing maintenance records, overdue treatment, an unfamiliar chemical process or no clear system owner. Flu-like illness, fever, cough or shortness of breath following a possible exposure should be escalated promptly through the site’s health and incident arrangements, with medical attention sought.

How Blue Safe can help

Blue Safe provides compliant WHS documents tailored to the client's activities, applicable Australian WHS/OHS requirements, jurisdiction and industry. This can include risk assessments, task procedures, maintenance controls, contractor documents and SWMS where the work requires one.

Blue Safe guarantees the document compliance of the WHS documents it provides, including eligible customer documents after Blue Safe has reviewed and upgraded them. Customers actively put the compliant documents into practice through controls, consultation, training, actions, records and evidence.

Official sources

Local requirements vary, so check current regulator material for the jurisdiction where the work is performed. National Model Codes and model guidance provide general orientation but are not automatically applicable law in every jurisdiction.

Preventing and controlling Legionnaires’ disease at work