Legionnaires’ Disease and air conditioning: A risk you probably didn’t know about |

Legionnaires’ disease is a type of severe pneumonia caused by a bacteria called Legionella pneumophila. It affects your lungs, causes high fevers, cough, muscle aches, and shortness of breath, and in some cases, it can be life-threatening, especially for older adults, smokers, and those with weakened immune systems.Most people don’t walk around knowing what Legionella is, but it’s more common than you think. The bacteria live in water, and they love warm, stagnant environments. Think hot tubs, fountains, plumbing systems, and yes, air conditioning units, especially large, industrial ones like those found in hotels, hospitals, office buildings, and shopping centres.
How does air conditioning spread a lung infection?
Here’s how it works:Air conditioners, particularly large systems with cooling towers or water tanks, can create the perfect storm for Legionella bacteria to grow. When the water inside these systems isn’t properly cleaned or maintained, the bacteria multiply. Eventually, microscopic water droplets (aerosols) get released into the air through vents or mist.Now, if you breathe in those contaminated droplets, you’re exposed.It’s not contagious (you can’t get it from someone coughing on you), but you can get sick just by being in the wrong building with a poorly maintained AC system.There have been several Legionnaires’ disease outbreaks linked directly to cooling systems. In fact, the disease got its name from an outbreak at an American Legion convention in Philadelphia in 1976, where over 200 people got sick and 29 died, all traced back to the hotel’s air conditioning system.Since then, there have been multiple outbreaks. Any place with a big HVAC system and stagnant water is a potential breeding ground if not properly maintained.
How do you know if you’ve got it?
Symptoms usually show up 2 to 10 days after exposure. It often starts like the flu, fever, chills, headaches, but then turns more serious. If you develop shortness of breath, chest pain, coughing up mucus, or feel like you’ve been hit by a truck, it’s time to see a doctor.Doctors can test for it and treat it with antibiotics, but early detection is key. If left untreated, especially in high-risk people, it can be dangerous.
How to stay safe
If you’re a homeowner with a standard AC unit, relax—your home system isn’t the usual culprit. But if you manage a building, work in facilities maintenance, or travel frequently to hotels and public buildings, it’s good to be aware.Here’s what helps:Regular maintenance and cleaning of air conditioning systemsFlushing water systems regularly (especially in buildings that sit empty for a while)Using biocides or chemical treatments in large cooling towersMaking sure water doesn’t sit stagnant in any part of the HVAC systemAnd if you’re a guest at a hotel and the air feels weird or there’s a musty smell, that’s worth noting (or avoiding).Legionnaires’ disease isn’t super common, but it’s serious, and totally preventable with proper building maintenance. If you run a facility or spend a lot of time in hotels, hospitals, or gyms, it’s worth knowing how this illness spreads and what to look out for.