Oxygen monitors are available in a choice of two ranges, with either external or internal sensors. The monitors below include a sensor, instruction booklet, recorder plug, and screw driver. VICI Metronics offers the complete G-Cal line of small, portable monitors/alarms which utilize patented GCI electrochemical sensors for the detection of O2 and toxic gases such as CO, H2S, SO2, NOX, and NO2. These low-cost, battery-powered units are ideally suited as a personal monitor for field use, but have a sensor cable option for remote sampling. Monitors feature a preset audible and visible alarm, with the gas concentration displayed in ppm or as a percentage.