The optimal CO2 level for cannabis is 1500ppm, but there is typically between 300-400ppm of CO2 already in the air.  CO2 meters will tell you how much C02 is in the ambient area, but you may need to calculate how much CO2 you need to add to reach the optimal level. Calculating your CO2 needs is a two-step process that requires you to know the volume of your grow area. First determine the volume in cubic feet by multiplying the square footage of your space by the height of the room. Once you have the cubic size of your grow area, multiply it by 0.0012. This will tell you how much carbon dioxide you will need to supplement your room in order to reach 1500ppm. JUMP TO CO2 CONTROL