Determinations of vinyl chloride and chlorinated organic solvent concentrations at the breathing zone of the industrial workers employed at the vinyl chloride synthesis process have revealed excessive exposure to certain chlorinated compounds. The average exposures of the operators of the vinyl chloride synthesis apparatus have been found to be 13 MAC for vinyl chloride and 2.5 MAC for 1,2-dichloroethane. The operators of the solvent synthesis apparatus have been exposed to average concentrations of carbon tetrachloride up to 3.5 MAC, the corresponding values for the fitters being 4.5 MAC for vinyl chloride, 3.5 MAC for 1,2-dichloroethane, and 3 MAC for carbon tetrachloride.