GMI PS500 4 Gas Detector with built in pump has been "designed by the customers" to be easy to use, reliable and cost effective. This rechargeable PS500 is set up to monitor Oxygen, Flammables, Carbon Monoxide and Hydrogen Sulfide. Unit has built-in sampling pump or selectable diffusion mode. User settable alarms with latching, go/no go options and datalogging included. Easily field servicable with no factory service required. Easy calibration using any manufacture's calibration gas. 3 meter sample draw hose and battery charger included. Two year warranty covers instrument and sensors.