HL-OC is a precise desktop gas monitor for monitoring oxygen (O2), carbon dioxide (CO2) concentration, temperature and relative humidity in the ambient air. It has been designed to protect the safety of peoples in dangerous work places. It will continuously display the ambient concentration of oxygen, carbon dioxide and activate its audible and visual alarms whenever the preset set points are exceeded. HL-OC can be widely used in the car, touring car, garage, food/fruits/goods container, petrochemical, power plant, telecom, medicine, mine, heavy industry, food industry, gas industry, and other confined spaces for personal safety. It can also be widely used in the houses, office, school, meeting room, restaurants, hospitals, mining facilities, metal refineries, commercial and public buildings, agriculture green house, and other places where carbon dioxide monitoring in confined spaces for personal health and personal comfort is important. HL-OC uses two-electrode electrochemical and Dual Beam Non-dispersive infrared (NDIR) technology, operating by the diffusion principle, for determining the concentration of oxygen and carbon dioxide respectively in air samples. HL-OC can implement ambient air calibration (20.9% and 400ppm CO2) when needed (such as annually). It has two alarm setpoints: Warning (O2: 23.5%, or >5000ppm CO2) and Danger (O2: 19.5%). Oxygen Sensor Specification: O2 Measurement Range : 0 ~ 30.0% vol. O2; O2 Resolution : 0.1% vol.; Sample Method : Diffusion; Temperature Range : -20 to 50°C (-4°F ~ 122°F); Humidity Range : 5 to 95%RH; O2 baseline Drift (-10-50°C) :