Wow thanks guys that's nice of you.

Zero: I still have not found a calculation that works to determine precisely how much coal it takes. Do your self a favor and check it every week or so incase the smaller amount does not last very long. All I know for sure is one 7x7x7 grow room stay's clean and fresh smelling for about 8 months with 15 pounds. A garage size room uses 20-25 pounds of coal. After 6-8 months the odor starts back itâ??s sweet fragrant odor. Very small amount at first but it does come through. I change mine once a year so far anyway.