A low-cost, four-gas portable detector featuring one-button calibration, easy-to-change sensors, rugged construction with excellent resistance to dust and water penetration, and a 16- to 20-hour run time. With an internal pump and charger included, this multigas detector is priced below most competitive four-gas detectors now on the market. Detects O2, H2S, CO and combustible gas and is used for confined space entry in industrial, agricultural and other environments as well as by fire and rescue personnel. Accommodates either NiMH or alkaline batteries, which are interchangeable.