Available to measure from higher concentration (vol %) to lower concentration (% LEL). Available to measure HC/O2, CH4/O2 in N2, inert gas and air with a reliable NDIR method. Sampling method: built in sample pump. Response time: within 30 seconds (T90). Ambient temp/ humidity: -10°C ~ + 40°C, below 90% RH, non-condensing. Continuous operation: approx. 40 hours (no alarm or light, at 20ºC). Power source: 4 "C" alkaline dry cell batteries or optional Ni-Cad. Dimensions and weight: 3.1 x 7.9 x 5.6 inches, approx. 2 kg.