Many growers overlook the huge importance of CO2 to fast growing plants.
CO2, along with light, are the two most important sources of food for plants. Plants take light and CO2, and through a process called photosynthesis, produce food for themselves. The nutrients that growers feed their plants are kind of like the salt and pepper, whereas the light and CO2 are like the meat and potatoes. The nutrients are necessary for photosynthesis to occur, but they are mainly a catalyst to allow the reactions to take place. In fact, if you were to analyze any plant, you would find that it consists of over 90 percent water, a few percent nutrients, and the rest is carbon.
Normal CO2 levels are between 300 to 500ppm (parts per million), depending on whether you live in an urban or rural area (we have almost 600ppm of CO2 here in Los Angeles!). Increasing these levels to 1500ppm can often have dramatic effects on your plants, including faster growth rates and increased yields. This is why it is so important to always have fresh air circulating into your grow room, or better yet, add supplemental CO2.