The MSA type GMA chin style common organic vapor canister was tested against nine hazardous vapors in a controlled access laboratory under conditions similar to the most severe expected operating conditions in the field. The vapors tested included chloroform (67663), benzene (71432), epichlorohydrin (106898), acrylonitrile (107131), propargyl-alcohol (107197), 1,2-dibromoethane (106934), acrolein (107028), chloromethyl-methyl-ether (107302) (CMME), and N- nitrosodimethylamine (62759) (NDMA). The challenge concentration was 50 times the assigned threshold limit value (TLV) or 50 times the lowest practical concentration where no TLV was assigned. A flow rate through the canisters corresponding to 49 standard liters per minute was used. Tests were conducted at relative humidities of 80 percent and less than 15 percent, and all tests continued for 16 hours or until 1 percent penetration or half the TLV was detected downstream of the canisters. A moderate breathing rate was assumed. The canister, under the experimental conditions, afforded adequate worker protection against chloroform, benzene, and acrylonitrile for a minimum of 4 hours and epichlorohydrin for at least 8 hours. The canister provided adequate worker protection for propargyl-alcohol, 1,2-dibromoethane, and acrolein for a minimum of 16 hours. Sixteen hour protection was also adequate for NDMA at the 1 part per million challenge level. The author recommends that the canister not be used in a CMME environment.