THE EFFECT OF VAPOR POLARITY AND BOILING-POINT ON BREAKTHROUGH FOR BINARY-MIXTURES ON RESPIRATOR CARBON

This research evaluated the effect of the polarity of a second vapor o n the adsorption of a polar and a nonpolar vapor using the Wheeler mod el. To examine the effect of polarity, it was also necessary to observ e the effect of component boiling point. The 1% breakthrough time (1% t(b)), kinetic adsorption capacity (W-e), and rate constant (k(v)) of the Wheeler model were determined for vapor challenges on carbon beds for both p-xylene and pyrrole (referred to as test vapors) individuall y, and in equimolar binary mixtures with the polar and nonpolar vapors toluene, p-fluorotoluene, o-dichlorobenzene, and p-dichlorobenzene (r eferred to as probe vapors). Probe vapor polarity (0 to 2.5 Debye) did not systematically alter the 1% t(b), W-e, or k(v) of the test vapors . The 1% t(b) and W-e for test vapors in binary mixtures can be estima ted reasonably well, using the Wheeler model, from single-vapor data ( 1% t(b) +/- 30%, W-e +/- 20%). The test vapor 1% t(b) depended mainly on total vapor concentration in both single and binary systems. W-e wa s proportional to test vapor fractional molar concentration (mole frac tion) in mixtures. The k(v) for p-xylene was significantly different ( p less than or equal to 0.001) when compared according to probe boilin g point; however; these differences were apparently of limited importa nce in estimating 1% t(b) for the range of boiling points tested (111 to 180 degrees C). Although the polarity and boiling point of chemical s in the range tested are not practically important in predicting 1% t (b) with tile Wheeler model, an effect due to probe boiling point is s uggested, and tests with chemicals of more widely ranging boiling poin t are warranted. Since the 1% t(b), and thus, respirator service life, depends mainly on total vapor concentration, these data underscore th e importance of taking into account, the presence of other vapors when estimating respirator service life for a vapor in a mixture.