Pressure drop and service life predictions for respirator canisters

Respirator canister designers and manufacturers have a responsibility to provide canisters with increasingly higher capacity and longer service life due to rising safety standards in the workplace. Optimizing the service life of conventional canisters is not about simply increasing the depth of adsorbent present in the canister because this will lead to an increased resistance to airflow, and a greater physiological burden on the user. To optimize canister design it is necessary to establish how the physical dimensions of the adsorbent bed affect breathing resistance and adsorption performance. The study presented in this article investigated both the pressure drop and cyanogen chloride chemisorption performance of a granular activated carbon adsorbent. Results obtained show relationships that correlate adsorption performance and pressure drop to the quantity of adsorbent, the linear flow velocity, and, where applicable, the challenge vapor concentration. Altering the linear velocity by increasing cross-sectional surface area has a more beneficial impact on canister performance than altering the adsorbent bed depth. The application of these relationships to the design of canisters is demonstrated.