A method for filtering a gas includes passing a gas into a compartment of a casing that includes a polymeric film, the casing having: a first sleeve having a first outlet opening, a first filter being at least partially disposed within the first sleeve so that gas passing through the first sleeve must pass through the first filter; and a second sleeve having an second outlet opening, a second filter being at least partially disposed within the second sleeve so that gas passing through the second sleeve must pass through the second filter, the second sleeve being closed so that the gas passing into the compartment of the casing passes through the first sleeve and the first filter and directly contacts at least a portion of the first sleeve comprised of the polymeric film but does not pass through the second sleeve. Opening the second sleeve when a predetermined condition is met so that the gas passes through the second sleeve and the second filter.