c556c467_egal__Cleaning___Sterilization_Pre_Anesthesia_Checklist_2008_Rationale
[Step] Calibrate, or verify calibration of, the oxygen monitor and check the low oxygen alarm. [Rationale] 
Continuous monitoring of the inspired oxygen concentration is the last line of defense against delivering hypoxic gas concentrations to the patient. The oxygen monitor is essential for detecting adulteration of the oxygen supply. Most oxygen monitors require calibration once daily, although some are self-calibrating. For self-calibrating oxygen monitors, they should be verified to read 21% when sampling room air. This is a step that is easily completed by a trained technician. When more than one oxygen monitor is present, the primary sensor which will be relied upon for oxygen monitoring should be checked. The low oxygen concentration alarm should also be checked at this time by setting the alarm above the measured oxygen concentration and confirming that an audible alarm signal is generated.
Anesthesia Gas Machine- Machine checklist, Medicolegal, Cleaning & Sterilization
Rationale