The objectives of this study were to determine the availability of portable direct reading carbon-monoxide (630080) (CO) meters, acquire selected meters and evaluate their characteristics, recommend the best use techniques, recommend performance standards, and recommend quality control standards. The procedure followed included a market survey, solicitation of meters, and evaluation of the meters selected. The meters selected for study included Bullard Portable CO Monitor, CO-Dackel, Ecolyzer Model 2800, EnMet Model PTM, Portable Carbon Monoxide Indicator Model-D, and Miran-I Variable Filter Infrared Analyzer. To be acceptable, a portable CO meter must have portability, a direct readout of CO concentration in parts per million (ppm) or a readout that is easily interpreted in ppm, recorder output, be simple to operate, come with instruction manuals, be inherently safe, be rugged, require sample conditioning as an integral part of the meter, and have easy zero and span adjustment. The following items were considered under performance characteristics: useful range, accuracy, zero drift, span drift, minimum detectable change, warm up time, response time operating humidity range, operating temperature range, and interferences.