The World's Biggest Frog

The "dust" you are seeing flying out of your forge isn't dust at all, it's coal ash. You need to jiggle the coal fire and move the coal to knock the dust down to the bottom of your fire pot, then jiggle the ash pot door to get the ash to fall into the ash pot before cranking up your forge blower. This won't eliminate all of the dust, but it will eliminate most of it. You need a good chimney system with a fan, or a good size hood to get the ashes and smoke to vent out of your shop. If you are getting large amounts of coal dust, by all means, get a dust filtration system in your shop. Coal dust even in small quantities is very explosive and you could end up blowing up your shop, your home <if you are home based> your family, and yourself. If you get fresh coal, always take the coal and sift out the dust and granules before using the coal. Coal factories actually pulverize some of their coal into a dust, then mix the dust with a small amount of water. Then when the mixture is the right consistency, will form the powdered coal into cakes and briquettes for coal fired stoves and furnaces. This is accomplished by very high amounts of pressure that generates just enough heat to fuse the dust together for making coal briquettes. The heat generated also allows for moisture to evaporate as the briquettes cool. Failure to remove all of the moisture from a coal briquette can cause it to rupture, pop and explode. If your coal has large amounts of dust, just be careful how you deal with it. There are plenty of other hazards with coal dust besides fire, including lung damage that can lead to "Black-lung Disease," especially if you are breathing in large quantities of both coal ash and coal dust. Black Lung was very common in the early days of coal mining. You can develop upper reparatory problems and serious sinus problems from breathing the dust and the ash, and it also contains certain carcinogens that can cause cancer. To clarify, Coal Dust is unburnt coal particles. Coal ash is coal that has already been burned, and all of the combustibles are mostly gone. These are the sparks and dust particles that you see flying out of your coal fire when you crank up the blower. Coal ash still resembles coal dust however, but is not as combustible as coal dust. It will burn, but at much higher temperatures than coal and its dust. Excellent question. Please be safe. I envy that you are able to use a coal fire to do your forgings...