The effect of airflow pattern on filter breakthrough in physical adsorption Original Research Article

The Wheeler–Jonas (WJ) model for prediction of the protection capacity of organic vapor filters under a fixed airflow was extended to breathing-simulation, pulsating flow. Breakthrough curves of dimethyl-methyl phosphonate (DMMP) and decane were measured under fixed flow and sinusoidal flow. A linear dependence of ln(CX/C0) on the breakthrough time (tB) was observed in all the experiments, indicating that the concepts of critical bed weight (WC) and dynamic adsorption capacity (WE) as defined by the WJ model are applicable to pulsating flow as well. WE was found to be almost unchanged by the flow pattern, whereas WC was considerably larger (by 7–44%) at pulsating flow compared to fixed flow with the same average rate. Thus, shifting from fixed flow to pulsating flow may shorten tB significantly. The effect of the flow type on tB increases with the ratio of the critical weight to the total bed weight. For a high protection level (C0/CX=60 000), the protection capacity of personal NBC canisters was reduced by up to 15% upon shifting from fixed to pulsating flow.