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Message: <blockquote data-quote="Nagol" data-source="post: 6940795" data-attributes="member: 23935">If we make a few assumptions to narrow down the effects:<ul> <li data-xf-list-type="ul"> We're talking grain dust.</li> <li data-xf-list-type="ul"> The dust has been milled with equipment closer to typical medieval quality than modern day quality.</li> <li data-xf-list-type="ul"> A kilo of dust is dispersed in an appropriate amount of air by a tool specifically designed for the job under near ideal conditions (no wind, limited humidity, complete dispersal)</li> </ul>Almost no damage really for anything portable by  a person.  The first dust explosion I could find on record was in a bakery in 1785 -- and that only blew out the windows of the shop.First, the particle size is almost certainly too big to create an explosion.  A diameter of <500 micrometres is required, but the sources I was able to find suggest ~700 micrometres was more typical for ground grains (I suspect that's why it hit a bakery first -- extra finely ground white flour for pastry).  Even if you did get dust ground finely enough, the lower explosive limit is 125 g /m^3 so 1 kg could cause an flash in 8 cubic metres or about a 5' cube (6' actually, but certainly not 10 -- that would require 8 kg or so).  True flour dust (as opposed to grain dust; stripped of bran) requires about half the density so if the society has the modern milling techniques you might be able to get the fuel down to 2 kg per shot to cover 10' cube.Next you have to get a tool that manages to disperse the dust enough -- but not too much! so that the dust is well distributed inside the flash cube.  This would be very tricky.  You need to get the dust suspended pretty evenly inside the target area.  A bellows-like contraption with dispersal nozzle might be able to do it, but it'd require a fair bit of tinkering I expect.And finally you have to apply a source to ignite it once the dispersal has reached its maximum.  Luckily, typical flame temperatures are enough to ignite grain dust so having a lit torch / open lantern as part of the tool would be enough. Though that's probably bad news to the operator as he will be at the edge of the flash at best and inside the flash at worst.Since we're not dealing with an confined space, you're much more likely going to get a flash-fire than an explosion.  There is nothing to contain the pressure until it builds up to something dangerous.So I'd say you're probably looking at something like up to 1d6 flame damage in a 5' diameter (Reflex save halves) using equipment that weighs ~15# and consumes 2# of flour per shot.  Probably an attribute roll would be necessary to use the device properly (Int, Wis, or Dex depending on how the DM conceives what is required to get the concentration right in the area); I'd go with something like Int DC 12 success and it works, failure and the action is wasted once you've tinkered enough to get the design worked out. And the operator would have to make the same save but get Advantage on it.</blockquote>

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