We can all agree that, with the exception of rain or maybe money, anything that falls out of the New York City sky is probably not something you want to land in your salad or any of your face's mucus membranes. The cold facts are that it's probably bird poop or subway slime or airborne urine, and getting it in your eyeball will likely lead to death or at least a severe case of dropsy.

One of the few exceptions to this rule is air conditioner water, which, on days like today, tends to shower freely down from window units city-wide. Don't worry, though: Slate explains that of all the things that can and probably will poison you from on high, air conditioner water is probably not one of them.

In most ways this water is exactly like rain (which also forms from condensed water vapor) or the moisture that collects on a cool can of soda, and it's typically no more harmful. However, in rare cases small amounts of water can be left to stagnate inside the air conditioner, making it a breeding ground for bacteria.

Which rare cases, you ask? The article goes on to detail an instance in 1976, in which many attendees of the American Legion Convention held at Philadelphia's Bellevue-Stratford Hotel fell sick after bacteria-filled air flowed throughout the hotel's air conditioning system. The disease was henceforth known as "Legionnaires' disease," and it doesn't tend to thrive on smaller A/C units. It does, however, spread through a number of other fascinating conduits. According to the Mayo Clinic, you can still catch Legionnaire's from hot tubs and whirlpools on cruise ships, decorative fountains, physical therapy equipment, swimming pools and water systems in hotels, hospitals and nursing homes.

The moral is that if you thought you were safe—well, looks like you need a splash of cold water to the face. Just don't get it from a hotel room. Or a cruise ship. Or a decorative fountain...