I'm seriously tired of people like you two arguing for no apparent reason. You were both right and wrong in a lot of aspects. First of the medical grower's Bible is not the end all be all for cannabis, in fact Jorge Cervantes DOES NOTE GROW AT ALL. he researches other growers. He has even stated this and High Times Magazine. In a closed, sealed, recirculating environment plants consume co2 and produce oxygen which is recirculated into the same environment that came from. When using regulators and pumps with co2 tanks, you Dial in the proper Ppm of co2 for the colime of plant foliage your room contains. The plants will then "breathe" this co2 and "exhale" FRESH oxygen. (speaking of which if you were to ceiling human into a closed environment with ENOUGH plants to compensate the human's oxygen consumption rate the gasses would exhange amd NEVER stagnate...theoretically speaking this sealed environment would be known as a manmade biome). As for flushing, generally speaking one should always flush. Regardless of whether using chemical nutrients or organic nutrients. Even if your smoke is not harsh, flushing will still bring out the dominant cannabis flavors, where is not flushing will bring out the flavors of either the organic or chemical nutrients used to grow this plant. I'm so sick of people like you two wasting bandwidth and time arguing with no resolution. there is no point in the two of you arguing when neither of you will change your minds. You want to believe what you want to believe regarding your own opinions, whether you are right or wrong. However, I digress. I apologize for my rant, I only meant to point out that you were both wrong and right in some aspect. Sealed environment's do not require venting whem regulated properly, and flushing although not NECESSARY is an excellent practice, which, when used properly brings out the full flavor and effect of the turpines in the cannabis plant. Please do some research before you waste people's time arguing for multiple pages on a thread thst doesn't belong to you.