The MaxO2 A patented ergonomic design fits comfortably in your hand and features a simple, one-touch on/off and calibration. The MaxO2 A will calibrate to room air (20.9%) or 100% oxygen. 24 month warranty on the analyzer and internal MAX-250 Long Life Sensor. 5,000 hours operation on 2 AA batteries. The Max02 A meets NFPA 99 requirement for an oxygen analyzer used to verify the effectiveness of a nitrogen purge.