Estimating service lives of organic vapor cartridges III: multiple vapors at all humidities.

A published model for estimating service lives of organic vapor (OV) air-purifying respirator cartridges has been extended to include multiple organic vapors at all humidities. Equilibria among the OVs are calculated using Ideal Adsorbed Solution Theory, whereas the effects of adsorbed water are considered as due to micropore volume exclusion. Solubilities of OVs in water must also be taken into account. Adsorption kinetics of components of mixtures are based on published correlations of the effects of covapors and water vapor. The dynamics of adsorption and competition are incorporated using expanding zones within the carbon bed, taking into account vapor and water displacements. Measurements of breakthrough curves for two ternary OV mixtures at high humidities have been done for a single cartridge type. The service life estimation model, implemented as a spreadsheet and a computer program, has been tested against these data as well as data for OV mixtures from literature sources. Good agreements were obtained between model predictions and experimental breakthrough times at dry conditions and humid conditions.