Inline filter mounts in most driver air systems to remove dangerous carbon monoxide from cockpit. Unit includes two vacuum sealed filter bags (used one at a time, typically one per event) that must remain sealed until ready for use. Keeping filter bag in a sealed zip lock bag between race sessions will prolong effectiveness (6 hours max. once removed from vacuum sealed sleeve.) After 6 hours of exposure, discard filter bag and replace with a new one - even if a zip lock bag was used. A freshly opened filter bag will be slightly saturated with a gel-like substance that can also be felt inside the bag. After six hours of exposure, the gel-like substance will have completely evaporated leaving only the dried foam agitators.