Space Station slowly losing pressure
2 mm a day is not real serious, considering 1 atmosphere is 760 mm, but considering the NASA transport problems, this is nothing to sneeze at either. If the ISS has an air volume of about 15,000 cu. feet, then 2 mm a day corresponds to about 40 cubic feet of air gone per day.
Naturally, this rate of leakage will not be constant as pressure goes down, and if they can pump enough oxygen into the air, they can get by on a little over half an atmosphere. I have no idea if it is mechanically possible to modify the air mix on the ISS.