A method for maintaining the enclosed volume of a sealed package at about ambient pressure, wherein the package contains a pressurized container comprising a drug, and an HFA (hydrofluoroalkane) propellant selected from the group consisting of HFA 134a and HFA p227, or a mixture thereof; wherein the method comprises the steps of (1) positioning an effective amount of a HFA adsorbent material, and said pressurized container, within a sealable package; (2) sealing the package so that the pressurized container and adsorbent are in an enclosed volume within the package at a pressure equal to about ambient pressure; and (3) adsorbing any leakage of the HFA propellant into the HFA adsorbent material so as to maintain the enclosed volume at about ambient pressure.