Organic Vapor Dosimeter

The concentrations of a wide variety of organic compounds present in working environments may be determined easily and inexpensively using diffusion dosimetry. Personal and area monitoring, resulting in data similar to that obtained with charcoal tubes, are accomplished without using pumps. A small lightweight dosimeter containing carbon sampling strips is exposed for a specific time period, usually 8 h. The front carbon strip adsorbs the organic vapor at a fixed, known sampling rate, which is dependent on the diffusion rate of that particular organic vapor. After exposure, the organic compound is desorbed from the carbon strip, usually in carbon disulfide, and analyzed by gas chromatography. Knowledge of the exposure time, the sampling rate, and the chromatographic result allows the time weighted average (TWA) concentration of organic vapor to be calculated. A back-up carbon strip in the organic vapor dosimeter insures that the capacity of the sampling section has not been exceeded. The dosimeter was calibrated and evaluated with gas concentrations generated using syringe pumps or vapor pressure methods. Air velocity effects have been studied as well. The organic vapor dosimeter proves to be a convenient alternative to charcoal tubes for the determination of many organic vapors in the workplace.