The Sentinel VCG-6 Variable CO2 Generators lets you choose the output of either 3 or 6 cubic foot CO2 per hour. 

Available in both Propane and Natural Gas, the VCG-6 Variable CO2 Generators are the safest and most advanced CO2 generators available in today's marketplace.

The VCG-6 Variable CO2 Generator comes standard with 2 pre-installed brass burners. These burners are designed to burn clean and produce consistent blue flames.

Tip-over switch shuts off the gas flow in the event the unit falls or tips over!
Dual redundant low-voltage solenoid valves to add a second layer of safety.
Solid state electronic ignition control module eliminates the need for pilot flame.

Rugged powder coated steel enclosure will last years. Comes complete with 10' hose and appropriate pressure regulator. Suggested CO2 level for a grow room is 1500 PPM.

Dimensions: 17.7" high x 10" wide x 10" deep
CO2 tank NOT included.

More info (PDF format)