CO2 Carbon Dioxide supplementation

[daddydoall]

Wonder if anyone with knowledge, expertise, or experience have thoughts / experience with CO2 supplementation. Recent article in latest AOS magazine suggests benefit in sealed greenhouse in Winter. My understanding of CAM (crassulacean acid metabolism) is that plants like orchids (and tillandsia, cacti etc) respire (uptake CO2 and release O2) only when STOMA are open which is usually at night(They hold their breath all day). In C3 metabolism found in common plants CO2 markedly enhances growth when plants are warm and growing (this is why it is commonly used in indoor pot farms). But what of C4 plants? Seems to me it would make sense to burn a candle or alcohol burner in a sealed GH in the evening when the GH vents are typically closed and orchids are respiring (the article suggested in daytime) if at all and only if it is warm enough and bright enough that plants are growing. I would expect less benefit in the winter in an unheated GH as the benefit of supplemental CO2 is strongly temperature dependent at least in common C3 plants. So maybe I'll light a 6hr votive candle each evening in my GH to supply extra CO2? Of course this will hardly be an experiment since I only have one GH. Hence this thread.
Happy growing!