Effects of humidity and contaminant concentration on respirator cartridge breakthrough.

A model described previously was developed further to examine the effect of both test humidity and contaminant assault concentration on respirator cartridge service life. The model emphasized the characterization of cartridge performance in the range of 0% to 50% breakthrough. This study specifically addressed a contaminant concentration range of 250-2000 ppm and test humidities ranging from 0% to 80%. The preconditioning humidity was fixed at 50%. The compounds studied were benzene and methyl chloroform. Two parameters, k' and tau, were described and values of these parameters were determined for each of several different sets of experimental conditions. The determined values of k' and tau were applied using derived expressions to generate each of several complete breakthrough curves for benzene and for methyl chloroform at specified contaminant assault concentrations and test humidities. The effect of humidity on the value of an additional theoretical parameter, a, was investigated. Values of this parameter and the parameters, k and K", were determined for specific test conditions. These values were substituted into pertinent expressions to produce a complete set of breakthrough curves (each curve corresponding to a particular contaminant assault concentration) for a given compound at a fixed test humidity. Several examples of breakthrough curves were generated for methyl chloroform. The results derived from the study agreed with corresponding experimental data.