The cremation chamber, which is just big enough to accommodate one body at a time, looks a bit like the inside of a pizza oven and can reach temperatures of 2,000 degrees Fahrenheit (1093 degrees Celsius). It's lined with a heavy duty, high density fiber brick designed to retain heat. Those bricks eventually wear out with repeated expansion and contraction and are replaced once they are worn down to about half their original thickness [source: Schaal].
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Industrial cremators can run anywhere from $80,000 for a basic, entry-level model to $250,000 for the latest models [source: Sullivan]. The modern-day incinerators are usually automated or computerized and can be programmed to adjust the temperature as needed. They burn natural gas, propane or diesel instead of the coke and coal that fueled retorts as late as the 1960s, allowing for more efficient and hotter burning while leaving little odor or smoke.
During the burning process, a second column of flame is fired up in a secondary chamber to burn off any particles or dust in the air leaving the retort, in order to reduce emissions, smoke and odors. Some retorts also have a wet scrubber in the emissions stack that sprays a mist of water so that escaping particles become trapped [source: Sullivan].
Once the body is completely burned, the chamber is then cooled and the cremated remains, which are often still recognizable as human skeletal remains, are swept with a long-handled hoe or wire-bristle broom into a tray. A powerful hand-held magnet is run through the ash to pick up metal parts left behind, such as fillings, plates and hip replacements, which can interfere with the grinding process. The metal parts are disposed with other biological material or recycled [source: Ellenberg]. The bones and remnants are put into a grinder, or cremulator, that uses ball bearings or rotating blades, like a blender. The remains are pulverized and poured into a plastic, lined container or an urn of the family's choice.
If the family requests, the ashes can be mailed via United States Postal Service, which requires a sift-proof box and signed confirmation upon receipt. UPS and FedEx don't ship ashes [source: Harris].
While there may be some inevitable residue mixing, the bodies are burned one at a time to ensure the separation of the cremated remains. Often, a disk identifying the person will be included with the remains throughout the process. Identification papers that travel with the body are placed on the outside of the incinerator and the box of ashes is also tagged and identified to avoid a mix-up.
Next, we'll find out who oversees crematories and some of the scandals that pushed lawmakers to beef up the rules.