One of the limiting factors in the speed of plant growth is the level of carbon dioxide (CO2) in the air in the grow room. Plants breath in CO2 and exhale oxygen as part of the photosynthetic process. A hydroponic intake/extraction system will draw fresh air into the grow space, thereby replenishing the CO2 levels in the air. However, the optimum carbon dioxide level for the fastest plant growth is far higher than normal levels in nature. See our blog article about this for details.