Residual Lifetime Indicators for Respiratory Cartridges and Canisters: Challenges and Opportunities for Sensing

Canister-based air purification respirators are frontline personnel's first point of defense against airborne contaminants. Tremendous advancements in filtration and purification materials have occurred in recent years, particularly with the advent of multifunctional, high-surface-area materials. Despite these, a significant challenge remains for canisters, and that is knowing when, without a doubt, they should be replaced. Residual lifetime indicators (RLIs) are essential for informing wearers when to make an active decision to replace their canister. RLIs can also be used to inform policymakers of appropriate changeover schedules, thereby reducing the wearer's risk of becoming exposed to airborne contaminants. This paper discusses some of the challenges with current changeover approaches and examines key issues for incorporating RLIs into canister respirators. A variety of sensor technologies and methodologies are examined, along with some recent RLI developments in the research and patent literature. A discussion on the challenges for making RLIs more amenable for incorporation into canisters is provided, along with recommendations for future development.