Features an integrated O2 Sensor for greater reliability, and is ideal for homecare and nursing home use. Oxygen Analyzer, Comes Complete W/ Sensor, Concentrator Adapter And Aerosol Adapter. Simple One Button Calibration. Replaces Cerom25A O2 Analyzer. The Sensor And Battery Can Be Replaced. Needs To Be Calibrated Weekly. 2 Year Warranty On Unit & Sensors. Sensors Typically Last 2-3 Years. The Vendor Does Not Have Suggested Recommend A #How Often# To Change Them. Just Replace If Sensor Goes Out." Case Pack 1