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Tech Tips:

Often in commercial HVAC and refrigeration, you'll come across a sight glass/moisture indicator on the liquid line. (Oil sight glasses also exist, but those are different from what I'm talking about today.) Sight Glass The sight glass portion is simple; it's just there to show if the liquid line has a full line of liquid […]

evelyneyarboroug
#moisture #sight glass #vaucuum

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this spooky Halloween short podcast episode, Bryan tells the story of the cooling tower killer: Legionnaires’ disease.

In the summer of 1976, the nation celebrated its bicentennial anniversary. The American Legion was holding its 58th annual convention at the Bellevue Stratford Hotel in Philadelphia, PA. In the days following the convention, doctors in Philadelphia started noticing dozens of Legionnaires in their hospitals with high fevers, chills, coughs, and difficulty breathing. Their symptoms resembled those of pneumonia, but patients deteriorated quickly, and antibiotics didn’t work as expected. People became more ill, and 34 of them died. There were many theories, from food poisoning to novel viruses to bioterrorist attacks.

The CDC investigated biological samples from patients and swabs from the hotel alike, but their findings were inconclusive. As news outlets sensationalized speculation over the cause of the illnesses, the disease was named after the unfortunate Legionnaires who suffered from it. However, the speculation would come to a close months later when CDC scientist Joseph McDade reviewed the samples and found a tiny, round-shaped bacterium living in the lung tissue of the victims. The bacteria would be named Legionella pneumophila.

Investigators traced the bacteria back to the hotel’s cooling towers. Cooling towers are essentially giant evaporative coolers and can create a mist. Legionella can thrive in the warm water of cooling towers, and the cooling towers dispersed the mist throughout the area, making hundreds ill. When water stagnates, bacteria can fester, but temperature is just as important as movement. As contractors, our maintenance procedures can save lives. In cooling towers, that maintenance entails regular cleaning, chemical treatment, and monitoring water temperature and flow.

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Legionnaires’ Disease: The Cooling Tower Killer – Halloween Short #263

10/28/2025

Bryan Orr

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