Legionella bacteria can infect humans and cause legionellosis and Legionnaires’ disease. The bacteria can grow on the wet surfaces of cooling towers, evaporative condensers (cooling plant) and scrubbers. Poorly positioned air intakes for air conditioning units can also capture the bacterial plume and draw it into buildings.
We have produced guidance for PCBUs that have cooling towers or evaporative condensers (cooling plant) on how to minimise or eliminate the risk of Legionella bacteria growing in their workplace.
Preventing Legionnaires’ disease from cooling towers and evaporative condensers provides advice on the roles, duties and extent of influence/control held by different PCBUs and guidance for installing a new cooling plant or maintaining an existing plant.
This fact sheet provides advice to persons conducting a business or undertaking (PCBUs) who have cooling towers or evaporative condensers (cooling plant). This includes (but is not limited to) cooling plant that is part of: any building air conditioning system, commercial premises with refrigeration plant (eg bulk storage of chilled or frozen food), or industrial process.
Legionella bacteria grow on the wet surfaces of cooling towers, evaporative condensers (cooling plant) and scrubbers, and can cause a pneumonia called Legionnaires’ disease. Legionnaires’ disease is often severe and can be fatal. Those at higher risk of becoming infected are adults over 50, males, smokers, people with lung disease or low immunity.
Legionella become airborne when fine water droplets (aerosols) carrying the Legionella bacteria are expelled from the exhaust fans of this equipment and may be inhaled by those nearby. Poorly positioned air intakes for air conditioning units can also capture the bacterial plume and draw it into buildings.
PCBUs whose work involves buildings, industrial or commercial premises that operate one or more cooling towers or evaporative condensers (cooling plant) must eliminate the risks from Legionella colonisation and dissemination so far as is reasonably practicable. If a risk can’t be eliminated, it must be minimised, so far as is reasonably practicable.
In relation to cooling plant, there will be different PCBUs with overlapping health and safety duties. When this happens, PCBUs must, so far as is reasonably practicable, consult, co-operate and co-ordinate activities.
The extent of the duty to manage risks depends on the ability of each PCBU to influence and control the matter. Table 1 describes the different types of PCBUs that may be involved, their duties and likely extent of their influence or control.
Role | Duty | Extent of influence/control |
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PCBUs who are designers, manufacturers, importers and suppliers of the plant and structures |
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Upstream PCBUs can influence and often eliminate health and safety risks through designing, manufacturing or installing plant that is safe for Designers of cooling plant are in a unique position in that they have the opportunity to eliminate or minimise risks by adopting the principles |
PCBUs who are installers, constructors and commissioners of plant and structures |
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PCBUs who manage or control the workplace |
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This PCBU has influence and control over who manages, maintains or services the cooling plant. This PCBU could carry out these actions themselves or contract someone else to do it.
For new buildings or renovations, this PCBU will have significant influence or control over the type of cooling plant installed. |
PCBUs who manage or control the workplace |
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This PCBU has influence and control over who manages, maintains or services the cooling plant. This PCBU could carry out these actions themselves or contract someone else to do it.
For new buildings or renovations, this PCBU will have significant influence or control over the type of cooling plant installed. |
PCBUs [DLM1] who manage, maintain or service the cooling plant |
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This PCBU has influence and control over eliminating or minimising the day-to-day health and safety risks from Legionella in cooling plant. They should have effective systems in place to maintain, monitor, treat and report on their sampling/testing/ reporting procedures. |
PCBUs who are solely tenants in buildings with cooling plant as part of air conditioning system |
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This PCBU is likely to have a a limited extent to influence or control the health and safety risks.
The extent of this duty will likely involve:
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Table 1: Different PCBUs with overlapping duties |
Recommended actions
Tables 2 and 3 describe recommended actions when intending to install new cooling plant, and when dealing with cooling plant on an ongoing basis.
Seek the views of your workers about the ways to eliminate or minimise the risks from Legionella in cooling plant.
When installing new cooling plant
Role | Recommended action |
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PCBUs who are designers, manufacturers, importers and suppliers of the plant | Design, manufacture, import and supply cooling plant:
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PCBUs who are installers, constructors and commissioners of plant and structures |
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PCBUs who manage or control the workplace |
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Table 2: Recommended actions when intending to install new cooling plan |
Note - Buildings (including their air-conditioning systems) must comply with the requirements under the Building Act(external link)
For existing cooling plant
Role | Recommended action |
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PCBUs who manage or control the workplace |
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PCBUs who manage, maintain or service the cooling plant |
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Table 3: Recommended actions for day-to-day operations |
Note - The Institute of Environmental Science and Research’s guidelines Environmental Sampling for Legionella Bacteria provide procedures for collecting samples from cooling plant for testing. These guidelines are available from: www.esr.cri.nz(external link)
Further information
Environmental Sampling for Legionella Bacteria - available from the Institute of Environmental Science and Research(external link).
The Prevention of Legionellosis in New Zealand: Guidelines for the Control of Legionella Bacteria(external link) available from the Ministry of Health.
NSW Code of Practice for the Control of Legionnaires’ disease available from the New South Wales Department of Health(external link) or download the PDF here [PDF, 1.7 MB].
The following standards are available from Standards New Zealand(external link)
- AS/NZS3666.3 Air handling and water systems of buildings – Microbial control – Part 3: Performance-based maintenance of cooling water systems
- NZS4302 Code of practice for the control of hygiene in air and water systems in buildings
- AS/NZS4020 Testing of products for use in contact with drinking water.
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