While most people are familiar with the word “Legionella,” very few know much about it. Legionella is a bacterium found naturally in freshwater environments like lakes and streams and can become a health concern when it grows and spreads in man-made water building systems. Legionnaires’ disease is a very serious type of pneumonia caused by Legionella bacteria.
It is not unusual to detect very low concentrations of legionella bacteria in the environment. Sometimes it is discovered in a building water system after there have been reported cases of Legionnaire’s disease. In these cases, it is quite possible that the bacteria had been present in the building water system, however, because of a low concentration, it was not creating a problem.
Earlier this summer, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) updated its guideline on controlling legionellosis. This update comes nearly 20 years after the previous version was published. ASHRAE Guideline 12-2020 is intended to help building owners manage the risk of legionellosis associated with centralized building water systems. According to ASHRAE, the guideline applies to hotels, office buildings, healthcare facilities, assisted-living facilities, schools, universities, commercial buildings, and industrial buildings. As stated in this guideline “eliminating uncontrolled growth of Legionella in building water systems is the central mechanism for managing the risk of disease. Complete elimination of Legionella bacteria from building water systems is difficult to achieve and typically not sustainable.”
I consider this new version of the guideline to be a vast improvement, offering very good technical guidance to the design, construction and building operations community. Anyone who is responsible for water systems in buildings should review it. A preview of Guideline 12-2020 is available on ASHRAE’s webpage, which I found to be a great benefit in advance of purchasing this document.