CO2augmentation is more involved than most people believe.
The CO2 must be administered ABOVE the plant (since CO2 is heavier then "air"), and you need a sealed environment, and a way to determine how much you're adding (too much is as bad as too little). The only way you can do this is with an atmospheric ppm meter; last time I checked they cost $500.00.
If you want to augment with CO2, about the only way you're gonna get any benefit is by spending $1,000.00 for a tank, regulator, emitter, ppm meter, fans and timers.
CO2 augmentation does not mean bigger or better buds. What is does is speed up vegatative growth by a week or so, depending on what kind of ventilation you have.
MUCH more cost-effective is to provide excellent ventilation (seperate powered intake and exhaust, cost about $20.00).
12 or so years ago I talked to a very experienced indoor grower.. I asked him if he had 1 bit of advice he'd give indoor growers, he said "more ventilation."
I thought to myself "what does he know" and went along my merry way.
And spent $1,000.00 for a complete CO2 set-up.
And now that equip. sits in my garage, gathering dust.
I got sick and tired of hauling that ******* tank over to the welding shop every 10 days to get it recharged. Instead I bought 2 bathroom exhaust-type fans from Home Depot ($10.00 each) and now there is a constant flow of fresh air in my growspace.
P.S. CO2 aumentation should not be done during lights out, and it provides no benefits past the first 3 weeks of flowering.