Oxygen sensors are used in enclosed spaces, vacuum test chambers, liquid nitrogen storage rooms, and other places where pressurized gases could lead to oxygen depletion. Because of their critical function, oxygen sensors are typically removed and manually calibrated by trained staff using a voltage meter in a 100% nitrogen environment —†a costly and error-prone procedure. The TR25OZ is an oxygen sensor that can be calibrated in situ with the press of a button, and with any gas of a known oxygen level.