The average level of CO2 in the atmosphere is about 300 ppm. If the level decreases down below 200 ppm in an enclosed area,plant growth slows to a halt. Through years of testing & research, the optimum enrichment level of CO2 for plant growth has been agreed to be about 1500 ppm. With Co2 enrichment, under good conditions, plant growth rates & flowering will increase 20-100%. CO2 can be used from seedling right through harvest. These user-friendly system will simply & automatically deliver cool, bottled CO2 to your plants for improved growth & higher yields. We offer a standard 0.2-2 CFH & high 1-20 CFH flow rate models. The ActiveAir systems include: regulator, with gauge, solenoid valve, flow meter, predrilled distribution hose, 24 hr - 30 minute increment timer & illustrated instructions. Tanks not included. Tanks for C02 can be purchased or rented at your local fire extinguisher, beverage or welding supply company.