On a hot muggy day water drips from window air conditioning units and you may accidentally inhale this drizzle or it may get on your clothes.
As a general rule the dripping water is sanitary and is just condensed water vapor that comes from the air inside the building. Window air conditioners are designed to drain water from the back and in most cases the water is exactly like rain and typically isn’t harmful.
However, in rare cases small amounts of water can be left inside the air conditioners, making a breeding ground for bacteria.
Water drips from the coil into a condensate pan and then exits the unit through a drain or tube, however a clog in this drain or tube can leave water to accumulate inside, which is an ideal place for many types of harmful bacteria.
In particular, a 1976 outbreak of Legionnaires’ disease was caused by bacteria that spread out of the air conditioning system at Philadelphia’s Bellevue-Stratford Hotel, that’s how the disease got its name because many of the victims were attending an American Legion convention.