Side Blast Forge, Coal Gas Explosion! in Shop Safety Posted January 1, 2020 Thank everyone for identifying the cause of my forge explosion, (I have been formally initiated into a large Forge Explosion Club). I ask very knowledgeable Blacksmiths about the explosion. (Interesting, that all experienced the same forge explosion under the same set of conditions.) The forge explosion is caused by adding green or wet coal over a hot fire and not running the blower. I received a response from this forum, Mark Aspery and from ABANA, Bob Valentine. All the responses are basically the same, keep the blower going when green/wet coal is added to the fire. The green coal over a hot fire will make a lot of smoke. The smoke is flammable and will burn the top of the fire. The flammable smoke coming off the top of the fire didn't cause the explosion, this smoke goes up the chimney or burns off. Explosion conditions: The input to the fire is the problem causing the explosion, adding green/wet coal with no air supply. Coal gases formed which is heavier than air so it settles in the lowest part of the forge system, the tuyere, flex air tube and blower. Turn the blower on and Boom! From what I have read since my explosion, the Bellows were always placed high above the forge. If the bellows were placed at or below the forge fire, the coal gas would no only fill the air tube but the large volume of the Bellows.. A Bellows full of coal gas made a very spectacular, damaging and deadly explosion Conclusion: To prevent the Side Blast Forge from exploding after adding green/wet coal , keep the blower running for a positive air flow. Using a plate over the fire hot spot increases the heat of the fire, ( something I have been doing this year with very positive results). The plate over the fire reflects some of the escaping heat back into the fire, making the fire hotter. I have been experimenting lately with using a Fire Brick over the fire which appearers to works a little better than the steel plate. If any one reading about covering the fire with a plate or fire brick, tried this procedure and have either positive or negative results, please respond to report your findings.