When you smoke around your plants, the smoke can cause the Stomata to close. The plant will not transpire propley and that will stunt the growth.

Justin - It's the blue flame that makes the usable CO² not a burn process when you burn anything there are other by-products that are bad for the plant that may be mixed with the CO². The whole idea of using CO² is raising the level above 1500ppm and hold it there for hours so the plants can asorb the extra amount.