AST Model SRX-CT-12 Oxygen Sensor is a galvanic type micro fuel cell specific to oxygen, designed for respiratory gas analysis. This sensor is a drop-in replacement to Envetec OOM202, City Technology MOX-9, AII PSR-11-917-M2 and Maxtec Max-12 sensor. Each AST Model SRX-CT-12 oxygen sensor is tested at 30 inches of water column pressure for any gas leakage. Proprietary electrolyte formulation and anode structure ensures full utilization of Pb anode, thus providing longer life without signal drift thus minimizing periodic calibration requirement. AST brand sensors are designed, developed and manufactured in the USA.