C02 Application to plants

Guys I have access to an unlimited supply of C02. 20lb cylinders. I know that plants thrive for and in a c02 enriched enviroment. How much, and how long would I give my plants. Could I set the regulator on let say 1-5 psi and let it flow ? Or would that be to "rich" of an enviroment and oversaturate the plant and burn it ?
 
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