CO2 is essential for plant growth. It's the gas humans breathe out and plants breathe in. In an enclosed growing area, as plants use up available CO2, their growth will slow down and may eventually stop. Slightly increasing CO2 will not only maintain growth but dramatically increase it.
The average level of CO2 in the atmosphere is about 350 PPM (parts per million). Through years of practice the agreed upon optimum level is the 1200-1500 PPM range. You won't notice this slight increase in CO2 level but your plants will grow much faster.
