This is the input for that Halon gas that the drives where filled with while in operation. Halon gas is a deadly gas that is pumped into the drives that makes them fire-proof, if there was a fire, the room they where in would be filled with halon gas as well, giving any operators in the room only one minute to get out.
It is 100% inert but contain no oxygen so when it displases normal air we choke.