Legionnaires' disease is an infection of the lung caused by the Legionella bacteria. The bacteria causes a form of pneumonia. It can be fatal.​

Last updated: 19 April 2013

Legionnaires' Disease

Legionnaires' disease is an infection of the lung caused by the Legionella bacteria. The bacteria causes a form of pneumonia. It can be fatal.


The disease is caused by breathing in aerosols which contain Legionella bacteria. This bacteria is present in low levels in the environment, but can grow rapidly to dangerous levels in cooling towers and in warm water systems.


Legionella growth can be controlled by proper water treatment procedures and regular cleaning. Building owners and occupiers have the prime responsibility to properly install and maintain all water-cooling systems, air-handling systems, and hot and warm-water systems. These systems are known as "regulated systems" because they are regulated by the legislation.

Responsibilities of building occupiers

The proper installation, maintenance and cleaning of systems is a legal requirement under the Public Health Act 2010 and Public Health Regulation 2012. Building occupiers who fail to meet these requirements are liable to heavy fines or even imprisonment. Systems can be inspected at any time.

Design and construction

Location of air intakes should be carefully planned. They should be placed well away from exhaust discharges and cooling-towers to avoid cross-contamination. They should also be away from pedestrian areas. All air intakes should be above the ground to make sure that dust, rain and small animals don't get into them.

Ductwork should be graded to prevent water collection and should be thoroughly cleaned before the system begins operating.

Installation of a water cooling system or hospital warm water system must be notified to local government authorities, so that a local register of systems can be kept up to date. A fee for a new notification may apply.

Water treatment

All water-cooling systems can only be operated if they are equipped with a process designed to control microbial growth certified annually by a competent person and only if the process is in continuous operation.


Only "duly qualified" contractors can be engaged to install, operate and maintain regulated systems. The Office of Fair Trading licenses contractors who undertake this work.

Operating and maintenance manuals

All regulated systems are required to be equipped with an operating and maintenance manual. The manuals must include all details of inspections and servicing performed. Manuals and records must be kept on site.

Council registers

Local councils are required to keep a register of water-cooling and hospital warm-water systems installed on premises in their area. It is your responsibility to ensure that the council is provided with the necessary information.

Protective measures

All personnel should take great care when inspecting air-handling and water-cooling systems. If possible, the system should be shut down before sampling, and a respirator must be worn.

When an outbreak occurs

Approved procedures prepared by the NSW Ministry of Health will be put into action if an outbreak occurs. You may be required to submit a water sample to an Environmental Health Officer from the Ministry or local council.

Other documents

Technical details about microbial control are available in NSW Health's Code of Practice for the Control of Legionnaires' Disease.

Australian Standard AS/NZS 3666 "Air Handling and Water Systems of Buildings - Microbial Control" is in three parts and is the main standard governing Legionella control. It is available from Standards Australia on tel: 1300 65 46 46 or fax: 1300 65 49 49.

AS/NZS 3666 is adopted formally in NSW under the Public Health Act and the Public Health (Microbial Control) Regulation. This legislation also adds some further technical requirements.

More information

  • Public Health Act
  • In NSW call 1300 066 055 to talk to your local Public Health Unit
Page Updated: Friday 19 April 2013