Understanding Legionnaires' disease
Once again, distorted news sources havestarted screaming that air conditioners are causing Legionnaires’ disease, which has led many people to thinking they are at risk whenever they walk by a window air conditioner or a condensing unit.
Of course, the problem can be caused by infected cooling towers on some commercial buildings. But poor reporting doesn’t always explain this.
Legionnaires’ disease acquired its name in July 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia. Of the 182 reported cases, mostly men, 29 died. On Jan. 18, 1977, the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella, and the species that caused the outbreak was named Legionella pneumophila.
Really, it’s inaccurate to say that contaminated cooling towers are the only cause of the problem since the bacterium has been around in warm water through the ages and the resulting disease used to be simply diagnosed as pneumonia.
But why did the Legionnaires’ get it so prominently that the disease took the name? Because many old Korean War and World War II soldiers were heavy smokers so their lungs were compromised and back in 1977 they happened to all be in one place that was near a contaminated cooling tower at the same time.
The sad thing about this story is that thousands likely died from the disease long before the source in our industry was finally recognized because dirty cooling towers have been the norm since the late 19th century. The only reason anyone had to keep cooling-tower water clean was to prevent the resulting algae buildup from clogging the pumps. Many companies still don’t keep their cooling towers clean for the same reasons — it’s expensive and time consuming to do so.
But now — thanks to litigation — building owners and HVACR contractors are being reminded that there is an even greater financial risk if they allow cooling towers to make people sick to the point of death.
Understand that cooling towers are used on large buildings to remove the heat from large centrally-located air conditioners (most commonly called chillers) in the smallest and most efficient ways possible. So the warm glycol-water solution flowing from the condensing side of the chiller usually is directed to an outside cooling tower in a closed loop where fans blow across the pipes that carry the solution as water is sprayed on them, resulting in efficient evaporative cooling.
However, the outside water in a cooling tower is in an open sump, which is the place from which it is pumped, so no excess water is wasted. This water is, of course, warm and is an excellent medium for growing all sorts of bacteria where there is no antibacterial injection to keep it clean.
The problem? I am aware of no program to teach building owners, maintenance people or servicing contractors of the need to keep cooling-tower water clean. Whose problem is it? Insurance companies? Chemical manufacturers? Supply houses? Contractor’s associations?
It’s all our problem when it comes to the sickened people and the resulting lawsuits. The fact that Legionella is still being found in cooling towers and people are still dying from it almost 40 years after the problem was identified proves we still have important issues to address.