How to Prevent Legionellosis via Cooling Tower Cleaning

A couple of months ago marked the 35th anniversary of an outbreak of pneumonia among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia.  This was the first reported incident of Legionellosis, or Legionnaires Disease. It was determined that the source was the hotel cooling tower via the air conditioning system.

Legionella, the bacteria that causes Legionnaires disease, is commonplace and it normally isn’t an issue unless it becomes airborne. This can occur through a shower, hot tub, humidifier, or cooling tower.  When very fine water droplets containing Legionella evaporate, they leave the bacteria airborne and anyone breathing them in can become infected.  Healthy people don’t usually get sick, but weak and elderly people are susceptible. Some get very ill and a percentage of them can perish.

In any facility, a good sterilization program protects you and your customers.  If you have pools and hot tubs, keep on top of your chemistry. Submerge shower heads and faucet aerators in bleach.  If legionella is suspected in your hot water system, raise the water temperature to 140 degrees Fahrenheit for 35 mins — this will kill any legionella in the system — then flush the pipes.  Make sure to alert people not to use the hot water during this operation to prevent scalding accidents.

Finally, good cooling tower maintenance is key. Any legionella released by a tower is likely to find its way into the air handling system, just like it did 35 years ago.  OSHA has guidelines on sterilization and tower cleaning to help you create and/or update a reliable maintenance program. Of course, a supplier who sells chemicals can also be a valuable resource.

By staying on top of your HVAC maintenance, having a good plan and the right equipment, Legionaires Disease can be relegated to a footnote in HVAC history.

What else can you do in the meantime? Check out these resources:

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