AST Model SRX-CT-1 Oxygen Sensor is recommended for breathing air equipment such as ventilators, is a galvanic type micro fuel cell specific to oxygen, a drop-in replacement to City Technology MOX-1, Envetec OOM102, AII PSR-11-917-M, KRANZ MK50212. Each AST Model SRX-CT-1 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.