Lutron PO2-250 pen Type Oxygen Detector Meter looks like a pen, it is very easy to use, easy to carry and measures the oxygen with accuracy.     Features:     • Galvanic cell type for O2 sensor. • High reliability Oxygen sensor, not be affected by acidic gases like CO2. • Oxygen sensor with temperature compensated. • Data hold, to freeze the desired reading value. • Auto power off saves battery life.