This is an OXYGEN ANALYZER which is very accurate and easy to use. It is made with extra-large buttons so anybody can use this product even those with bad eyesight. The oxygen analyzer is designed to detect O2 concentration in %vol with balanced nitrogen (such as air) - not to be used in any other situation and the source must be pressurized. This is not an ambient O2 air quality monitor. This instrument will analyze and confirm oxygen (O2), flow (F) and pressure (P) coming from a . The analyzer is already calibrated so just Turn ON and GO! Includes the Gas Detector, English Manual, and charger. The product has a built-in lithium battery and is charged via the supplied charger +12VDC. Battery operation can last for over 24 hours. Sensor: Oxygen sensor, Sensor Life: >5 years, Oxygen (O2) Range: 21% - 95% (Error 24 hours, Expected Life: >5 years.