Any type of gas drawn from a gas tank becomes whatever type is currently in the buffer. This only applies to gas tanks, incorrect gases from pressurized pipes seem to be correctly blocked.

Place brand new chemical infuser. Take a tank of hydrogen and a tank of chlorine, and put them into the input slots just long enough for a trickle of gas to enter each buffer. Then remove them and put the hydrogen tank in the chlorine input and/or vice versa. Or place a sodium tank in both inputs. The mismatched gas will be drained and the buffer will fill, magically transmuting one gas into another.

Fixed, thanks!