There is a lot of news on Legionella this week. The bad news is that the bacteria is throughout our environment and it’s pretty easy to develop a colony in building water systems. The good news is that by following some basic preventative maintenance and operational guidelines, most situations that propagate the bacteria can be mitigated.
Major points to understanding both the threat that Legionella presents and how to reduce exposure include:
- Legionella pneumophila is present in most water sources.
- The bacteria thrives between 68 and 122 degrees Fahrenheit.
- Aspiration, or breathing in contaminated water is the primary mode of transmission.
- Public water is typically treated to provide 0.1 parts per million of chlorine, which is uninhabitable to the bacteria.
- Heating hot water to 140 degrees kills it in with 32 minutes, and 130 degrees takes 5-6 hours.
- The leading sources are domestic hot water systems, cooling towers, fountains and ice machines.
- A standard flushing PM incorporated into your housekeeping routine can be effective in preventing propagation.
- Flushing an unoccupied or partially occupied building prior to returning should be a priority.
Below are a few industry links to help you maintain a safe facility:
Guidance for flushing a building to return to occupancy can be found here.
Guidelines based on industry standards: ASHRAE 188P
Legionella risk management: ASHRAE Guideline 12
Professional help in developing a risk management and documentation program: Contact Brian Flannigan at Phigenics, www.phigenics.com.
Contributor: Stephen Oskin, PE, LEED AP, Director of Mechanical Engineering at Barton Associates.
