Cremation of a dead body is carried out at a temperature ranging between 1400 and 1800°F. The process takes place in a cremation chamber, also known as a retort, of a crematory. During incineration, the body is exposed to a column of flames produced by a furnace fueled by natural gas, oils, propane, etc. Next, the heat dries the body, burns the skin and hair, contracts and chars the muscles, vaporizes the soft tissues, and calcifies the bones until they crumble. The bodies are burned one at a time. Some crematories have a secondary afterburner to help burn the body completely. Otherwise, the cremation technician may have to crush the partially cremated remains. It is then collected in a tray or pan and allowed to cool. Non-organic materials, such as metal from fillings are removed before the next process because they may damage the equipment used for pulverization. Finally, the dried bone fragments are further ground into a finer sand-like consistency with a cremulator. On average, it takes about 1-3 hours to cremate a human body, thereby reducing it to 3-7 pounds of cremains.