If you're using fluorescent grow lights like CFLs or T5s, there's probably already plenty of CO2 in the air for your plants to process all the light they're being given
Things are different when there's more light being provided than your plants can naturally use. In high-light situations, supplying more CO2 can allows your plants to use more of that light, which results in increased photosynthesis.By getting your plants to produce more energy from the same amount of light, they'll reward you with faster growth and bigger yields! Aswell as an increased resistance to light and heat stress!
It's important to figure out how much CO2, if any, you should be providing before you start the process as CO2 is wasted with simple mistakes.
CO2 Supplementation Works Best With MH/HPS and LED Grow Lights!