1. Test Oxygen in the office, workshop, train, bus, mine, mountain, vessel cabinet ect. 2. With backlight, alarm with light and Features 1. Test Oxygen in the office, workshop, train, bus, mine, mountain, vessel cabinet ect. 2. With backlight, alarm with light and sound. 3. Low battery indicate 4. Easy operation Specifications: Range: 0~25%VOL Accuracy: ±0.5% Power: 3x1.5V AAA battery Size: ...