>considering smoke from kitchens as source for CO2<p>Mushrooms expel CO2 and intake O2; there are several products such as [0] but you could just as easily grow some edible mushrooms to raise CO2 within the enclosure.<p>[0] <a href="http://www.planetnatural.com/product/exhale-co2-bags/" rel="nofollow">http://www.planetnatural.com/product/exhale-co2-bags/</a>