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Middlesex-London Health Unit

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Cooling Tower Registration Project

The Middlesex-London Health Unit (MLHU) has established a Cooling Tower Registration Project to help reduce the risk of exposure to Legionella (a bacteria) to those individuals who live and work in our community.


What are cooling towers?

As defined by the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), “a cooling tower is an evaporative heat transfer device in which atmospheric air cools warm water, with direct contact between the water and the air, by evaporating part of the water. Air movement through such a tower is typically achieved by fans, although some large cooling towers rely on natural draft circulation of air.”1

Why is cooling tower registration needed?

Past Ontario Chief Medical Officer of Health, Dr. Arlene King, had advised of an increase in the number of Legionella cases reported each year in Ontario from 2010 to 2011.


A Cooling Tower

A picture of a cooling tower

Prevention of legionellosis in cooling towers is most influenced by engineering design and maintenance practices of equipment that can harbor Legionella. Health units have been asked to provide guidance information for the prevention of Legionella in cooling towers and other water systems within their communities.

The greatest challenge has been establishing which buildings or facilities are equipped with vulnerable systems. Searches within the City of London have shown that, other than health care facilities such as hospitals and residential homes, there are no agencies which maintain a list of this equipment.

In response to this, the Health Unit conducted a literature search of other programs within Ontario. The City of Hamilton and Hamilton Public Health Services took measures in 2009 to initiate a by-law which requires building owners and operators to register their equipment, provide a risk management plan and maintain a log of all information related to that equipment. In partnership with the City of London Chief Building Official, the MLHU has decided to work with building owners and operators on a voluntary basis.

As Public Health representatives we strongly urge that all cooling tower/system owners and operators ensure that their cooling equipment is properly maintained according to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and/or CTI (Cooling Technology Institute) industry best practices. See the Cooling Tower/System(s) Resource Materials web page for access to the standards recommended for use by these organizations.

What is the intent of the Cooling Tower Registration Project?

The intent of the Cooling Tower Registration Project is to have all cooling towers and systems registered with the Health Unit. In doing this we can:

  • Assist owners/operators in the development of a risk management plan,
  • Know who to contact during an outbreak, and
  • Provide educational materials to the systems operators.

Additional Information

For more information or questions about cooling towers and systems, or the Cooling Tower Registration Project, please continue to browse this website, or

Date of creation: April 11, 2013
Last modified on: January 3, 2018


1American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE). (2000). ASHRAE guideline 12-2000: Minimizing the risk of legionellosis associated with building water systems. Atlanta, GA: American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc.
2Government of Canada. (2015, May 14). Legionella.. Retrieved from
3Cooling Technology Institute. (2008, July). Legionellosis: Guideline: Best practices for control of Legionella.