The breakthrough time and adsorption capacity of respirator cartridges for organic vapors were examined. A previously derived mathematical equation that related breakthrough times to fractional breakthrough on respirator cartridges containing a carbon adsorbent was applied to adsorption data for 121 organic chemicals to calculate the time required for 50% breakthrough (T50), the weight of compound adsorbed at breakthrough percentages of 1, 10, and 100%, and times required for 1 and 10% breakthrough. The assault concentration of each chemical was 1000 parts per million (ppm), the temperature 22 degrees-C, and the flow rate 53 liters per minute. The calculated values were compared with experimental values where available. Calculated values of the rate constant for adsorption, T50, times required for 1 and 10% breakthrough, and the amount adsorbed at 1, 10, and 100% breakthrough were tabulated. The calculated values generally agreed well with the experimental values. The times for 1 and 10% breakthrough of methanol (67561) and methyl-chloride (74873) were negative indicating the breakthrough of these compounds occurred almost immediately and that charcoal was not a good sorbent for either. A more detailed analysis of the effect of the weight of adsorbed acetone (67641), benzene (71432), carbon-tetrachloride (56235), dichloromethane (75092), diethylamine (109897), hexane (110543), isopropanol (67630), methyl-acetate (79209), and methyl-chloroform (71556) on three types of carbon respirator cartridges using assault concentrations of 50 to 3000ppm was performed. Saturation capacity, as indicated by breakthrough, decreased with increasing assault concentration.