The Sentinel CHHC-4i is the most advanced CO2 controller available on the market today. It incorporates the proprietary S.I.C.E. ? Sentinel Intelligent CO2 Enrichment ? communication and control components and programming that are unique to Sentinel. It allows for communications between Sentinel S.I.C.E series products, providing a level of control never before seen in your greenhouse, garden or grow room. The system works by a Sentinel S.I.C.E. series controller, such as the Sentinel CHHC-4i, measuring and monitoring your growing environment. As the atmospheric CO2 levels change, the controller will tell the Sentinel ICG series generator to increase output, decrease output or go into idle mode...all computer controlled. As the optimal conditions are reached, the S.I.C.E. system can decrease Co2 output, making sure that the user defined optimal level is not overshot.