The modification and further development of a previously introduced theoretical model has been reported; the original model was designed to address respirator cartridge contaminant breakthrough problems. The previous theory was capable of generating only symmetrical, sigmoidal contaminant breakthrough curves. In this study nonsymmetrical breakthrough curves are addressed. The modification of the theory involves the introduction of a simple, linear, time-dependent expression for the saturation capacity of the respirator cartridge sorbent bed. The modified expression includes three theoretical parameters: k″, τ and Wa. The theoretical approach introduced assesses the effect (on contaminant breakthrough) of the relative humidity of both the ambient environment in which the respirator cartridge is used and the specific environment utilized to precondition the cartridge. With a single mathematical expression, it is possible to generate valid theoretical contaminant breakthrough curves for a wide range of environmental conditions. The specific values of relative humidity considered in the study are ∼0% (dry), 20%, 50%, 65%, 80% and 90%. The specific organic compounds addressed are carbon tetrachloride and benzene. Calculated theoretical curves (over the entire breakthrough range of 0%–100%) are compared with corresponding experimental data for several different humidity conditions at a fixed contaminant assault concentration of 1000 ppm and at a fixed respirator flow rate of 53.3 L/min. Agreement between theory and experimental data is satisfactory.
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Yoon et al. (1988) studied this question.