This card provided a place to record how many hours the respirator had been used since it was issued, or since the last filter change. Initially, the respirators were rated for 60 hours of use before the charcoal and soda lime filters needed to be replaced. By 1918, the replacement time was downgraded to only 40 hours. The respirators were regularly inspected by the battalion gas officer, and when the indicated number of hours were accumulated on the card, the filter canisters were removed and replaced with fresh ones. This work usually was done by the gas officer and the non-commissioned officers assigned and trained to assist with this duty. Any other repairs to the respirator were also recorded on this card. The card usually was tied to the respirator hose at the point where it attached to the filter canister.

The canisters were also replaced if they became soaked with water, which reduced the effectiveness of the filtering agents in the canisters.