1. unplug and remove circ fan from unit.
2. remove hot air duct plate on top of unit
3. block air gap in front of unit.
4. dump lots of hot water down the hole until it comes out clean where the circ fan mounts (for me its usually about 35 gals)
5. let air dry for a week. (the floor)
i think the only thing you can do is to unplug and remove circ fan and take a shop vac and suck out what coal dust or dirt that may get in there.
since the fan is only 135 cfm and doesnt produce a high head it doesnt have the power to blow anything much up there.
i have bits of coal that have found there way into the fan housing from spillage from filling the hopper. what i also know is when you pull the sifting pan out be careful not to spill any fines because that will get sucked up by both fans but not enough to go through the unit.