The CHAD® Evolution™ Electronic Oxygen Conserver delivers a uniform oxygen pulse at increments: 1-7 plus CF Preset at 2 LPM. Delivers a 5:1 savings ration from 14-40 breaths/minute. Operating pressure range: 200-3000 PSI. A single push button selects the equivalent LPM dosage settings and the auto shut-off features conserves battery life. Minimum battery life of 2 years (2 AA batteries).