Somebody did mention dust and the possibility of it burning. Yes, metal can burn. They are known as class D fires and are very difficult to extinguish. In the very unlikely event of you accidentally creating thermite there is no chance of extinguishing that fire, just get yourself to safety. Where I work we have aluminium dust and it has ignited and I dumped a CO2 extinguisher on it and it only burnt hotter. I knew putting water on it would cause an explosion, but the CO2 making it worse was a surprise. We now have a Class D extinguisher that works by surrounding the burning material with a sodium chloride shell. It does not stop the burning, it just stops the fire spreading. If the fire has already spread to an area larger that the extinguisher can handle then the fire cannot be extinguished.