Dear Kevin
I think it is pretty obvious that a fan-powered stove will loft a lot more small particles than a natural draft version. They can easily be blown up through the fuel bed. If it is chimney-type ND stove then it is not such an issue. Regards Crispin ++++++++ Dear Crispin Thanks very much for your helpful comments. Clearly, a chimney that vents products of combustion outside the Living Space is advantageous, compared to a stove system that vents into the Living Space. I was aware of the great importance of the size of the Particulate Matter. Basically, "big dirt particles" are not nearly as bad as are fine particles that can lodge deep in the lungs. Clearly also, "more bad-sized particles", with "bad type composition", are worse than fewer "safer sized particles", of "relatively neutral composition. The only way to "digitize the generalities" is with a scientifically sound test program that identifies and then measures the relevant parameters. Once numbers have been attached to the relevant parameters, then it is relatively easy to determine whether or not a given stove system is "safe" or "hazardous." Rice Hulls are very interesting. While they have a high percentage of highly siliceous ash, complete combustion could potentially make the ash available in a hazardous manner. In Paul O's case, where he is interested in char making, I would guess that most of the siliceous components would remain embedded within the char particles, in a safe and non-hazardous manner. However, some ash particles would be liberated in that some of the char would be burned in the pyrolysis process. Best wishes, Kevin
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