Potted,
I used the 'Exhale" on the grow before last and I could not tell the difference with or with out them. I read, some where, that more than the normal amount found in the atmosphere was not very helpful unless your plants were subject to high heat or high levels of infrared radiation (as growing at higher altitudes). Maybe the mycelium does not produce enough CO2 to make a noticeable difference in the plants growth. during the last grow, I was making dry ice hash and after I finished I placed the leftover chunks in a dish and placed them at the top of my grow room, just in case.