During the past two years, Union Carbide Corporation (UCC) has developed completely automatic systems for monitoring 0-25 ppm vinyl chloride monomer (VCM) in working atmospheres and for processing the data obtained. Each system includes a process gas chromatograph, a sampling system capable of monitoring up to 19 points and data processing equipment. The data systems compute and print out statistical summaries on shift, daily and monthly bases and estimate the maximum exposure to VCM for each job. These systems are now essential operating tools at several UCC production units.