Domnick Hunter hydrogen generators are a safe and economic alternative to high pressure gas cylinders. These generators deliver a continuous stream of 99.99999% pure hydrogen, suitable for use with any laboratory instrument requiring a supply of ultra high purity hydrogen, and ideal for carrier gas and fuel gas applications. domnick hunter hydrogen generators use a proprietary ion exchange membrane to produce ultra-high-purity hydrogen from laboratory grade deionized water, totally eliminating the need for caustic solution. These generators are designed for total safety and highly reliable operation. Hydrogen is generated only on demand, at low pressure, and minimal volume is stored within the unit. The unique digital display gives system status and diagnostic capabilities not available on any other competitive hydrogen generator. Model 40H Output flow 0 ‑ 250 cc/min.