A method to at least temporarily replace air with an alternative gas in a first disk drive having a breather filter port is disclosed. A first disk drive is placed in a chamber, which is then evacuated to establish a sub-ambient chamber air pressure. Air bleeds out of the first disk drive through its breather filter port during a first period, until an internal pressure within the first disk drive reaches a reduced internal air pressure that is less than one third the first disk drive's initial internal air pressure. The chamber is then filled with the alternative gas. The alternative gas bleeds into the first disk drive through the breather filter port during a second period, until the internal pressure within the first disk drive reaches a restored internal gas pressure that is in the range 0.5 to 1.25 times the initial internal air pressure.