The GasWatch 3 is the world's smallest and lightest single-gas monitor. Weighing just 1.6 ounces, its compact form affords great comfort and flexibility in how you choose to wear it. It can be worn on your wrist as a watch, or clipped into your breathing zone on your lapel, hard hat or other safety equipment with its alligator clip. The 5 different GasWatch 3 models can protect you from oxygen deficiency [GW-3(O2)], exposure to carbon monoxide [GW-3(CO)] or exposure to hydrogen sulfide [GW-3(H2S)]. A hydrogen compensated model [GW-3(C-)] can protect those who work in steel mills, refineries or other environments where hydrogen is present from carbon monoxide exposure. The dual sensor model [GW-3(CX)] can simultaneously protect you from oxygen deficiency and carbon monoxide exposure. A small, field-replaceable, coin-type lithium-ion battery gives the GasWatch 3 over 4,000 hours of continuous operation. The hydrogen compensated CO can operate up to 2,500 hours, and the dual sensor CO/O2 model will get up to 2,000 hours of continuous operation. The great battery life coupled with a 3-year warranty gives the GasWatch 3 tremendous value and a low cost of ownership. RKI Instruments GasWatch 3 w/ CO(-H2) Sensor, Alligator Clip 73-0025