Somewhere in West Texas is a 7-inch radioactive cylinder that Halliburton would like to find. Anyone who comes across it is advised to keep their distance.

The oil field services company lost track of the device, which is used to assess potential sites for hydraulic fracturing, on Tuesday (Sept. 11) while trying to transport it from Pecos to a well site near Odessa 130 miles away. A special unit of the Texas National Guard has now stepped in to aid Halliburton in a search for the cylinder, according to Bloomberg.

"It's not something that produces radiation in an extremely dangerous form," said Chris Van Deusen, a spokesman for the Texas Department of State Health Services. "But it’s best for people to stay back, 20 or 25 feet."

The tool that Halliburton lost contains a mixture of beryllium and americium-241, the same radioactive isotope of americium that is found in very small quantities in a common type of smoke detector.

"In the presence of beryllium, the alpha particles [emitted by americium-241] will react to form neutrons," explained Tom Hei, associate director of Columbia University's Center for Radiological Research. "For alpha particles, you can put a piece of paper in front of it and will provide adequate shielding. Such is not the case for neutrons, which require significantly more shielding or a longer distance from the source for adequate protection."

The neutrons emitted by the cylinder have a biological impact 10 times more powerful than X-rays and the distance at which they would be dangerous to humans would depend on how much of the radioactive material is contained in the device, Hei told Life's Little Mysteries.

According to the International Atomic Energy Agency's five-tier scale for categorizing radioactive sources, the americium-241/beryllium neutron sources used for assessing hydraulic fracturing sites are classified as Category 3 sources (Category 1 is the most dangerous).

The agency's explanation of a Category 3 source that hasn't been dispersed by fire or explosion reads: "This source, if not safely managed or securely protected, could cause permanent injury to a person who handled it or who was otherwise in contact with it for some hours. It could possibly — although it would be unlikely — be fatal to be close to this amount of unshielded radioactive material for a period of days to weeks."

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The Texas health department says the cylinder is stamped with the words “danger radioactive” and “do not handle” along with a radiation warning symbol. Anyone who sees it is advised by the department to keep away and notify local law enforcement.

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