If you went camping before 1990, there's a good chance you carried radioactive material in your gear. Those delicate mesh bags that make gas lanterns glow - called mantles - contained thorium dioxide, a mildly radioactive element that could actually register on radiation detection equipment.

In October 1980, a health physicist named Walter Wagner toured California's Rancho Seco nuclear power plant with a scintillation counter. When he held it near a Coleman lantern mantle he'd brought along, the device registered a measurable radiation signature. It wasn't enough to trigger facility alarms, but it proved these innocent-looking camping supplies were genuinely radioactive.

Why Put Radioactive Material in Camping Gear?

Thorium wasn't added to mantles by accident - it was the secret to their incredible brightness. When heated by burning gas, thorium dioxide becomes incandescent, producing a brilliant white light far superior to the flame alone. A typical mantle contained about 250mg of thorium (0.027 microcuries), though some contained up to 400mg.

The dose rates weren't apocalyptic. A single mantle measured 0.68 microsieverts per hour on its surface. An avid camper using a lantern every other weekend for a year would receive 3-6 microsieverts of radiation - tiny compared to the 2,400 microsieverts you absorb annually from natural background radiation.

The Radioactive Boy Scout Connection

The radioactivity became more concerning when concentrated. In 1994, 17-year-old David Hahn built a model breeder reactor in his mother's potting shed using materials including thorium ash from thousands of lantern mantles. Even after dismantling his creation, local radiation levels measured 1,000 times background levels.

Hahn had exploited a loophole: you could legally buy radioactive material by the mantle, and nobody tracked bulk purchases. His experiment drew national attention and highlighted the surprising accessibility of radioactive consumer products.

What Happened to Thorium Mantles?

Around 1990, major manufacturers like Coleman quietly switched from thorium to yttrium, a non-radioactive alternative that produces similar incandescence. The change was driven by public awareness rather than health concerns - the actual radiation exposure from normal use was negligible.

However, thorium mantles didn't disappear completely. Chinese manufacturers still produce them, though quality varies wildly. According to Coleman collectors who test mantles with radiation meters, some Chinese mantles are "hot" while others barely register above background levels. Without a Geiger counter, there's no way to know which type you're buying.

So while modern camping mantles are generally safe, vintage ones from the thorium era remain mildly radioactive. If you've got old camping gear in the garage, you might be storing a piece of radioactive history.

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