Using Oxygen Detectors for Measuring O2 Depletion Oxygen (O 2) depletion monitors are devices designed to measure ambient concentrations of atmospheric oxygen, alerting users when nearby Ievels have fallen. These alerts allow appropriate action to be taken prior to an evacuation being required due to potentially dangerous oxygen levels. Problems also arise when oxygen levels are too high. Oxygen ‘enrichment’ (levels over 23%) is potentially dangerous, leading to increased chances of combustion and the intensity of fires. Oxygen detectors are able to signal any potentially dangerous levels of oxygen, making them essential instruments in a wide range of applications. Understanding Oxygen Enrichment and Depletion