America throws out some six million window air conditioners every year, according to the Environmental Protection Agency. If yours will be joining those ranks as the summer winds down—maybe it’s broken, maybe after all this heat you’ve resigned to moving to the Yukon before June rolls around again—you should know that tossing an AC is not as simple as hauling the unit to the curb. In fact, it’s actually illegal to smuggle your AC to a landfill with the rest of your trash.

That’s because ACs contain refrigerant, which can contribute to climate change. In older appliances, these are chlorofluorocarbons (you might know them by their nickname, CFCs). Newer units contain hydrochlorofluorocarbons or hydrofluorocarbon. Yes, all of those names sound the same—don’t worry about distinguishing between the three of them, because they’re all pretty bad for the environment. All three act as greenhouse gases if released into the atmosphere, and with the exception of the last one, will deplete the ozone layer. If your AC winds up in a landfill with the refrigerants still inside, they will leak out and go into the sky and wreak havok.