Many companies introduce C02 into a hydroponic environment to grow red and yellow peppers into plants as high as 40 feet tall that produce year round harvests they yield demonstrably and measurably thicker and heavier organic material, with results of more pleasing looking vegetables that produce significantly greater densities of nutrition per pound.
The average, most predictable levels of C02 are around 600ppm.
Who’s afraid of CO2? Not me. As those plants are sucking up the co2 they’re giving up the oxy and greening the earth.
My pepper plants aren't doing quite that well. I'd be interested in reading more about this but I'll try to find my own links. I wonder if any of these techniques are usable by individual gardeners.