The developer of luxury prepper condos built in old US Atlas missile silos told Time magazine sales inquiries for his $3 million units have spiked 40 percent. And a bomb shelter builder in California reported he's sold 1,000 shelters for $25,000 each so far in 2017, according to the Chicago Tribune. Both credit fear over a nuclear exchange with North Korea.

However, the history of nuclear testing shows they are wasting their money.

It's true that remnants of nuclear events in far away places can be detected days and months after the events. For instance, nuclear remnants were discovered in the Pacific ocean off the U.S. west coast after the Fukushima nuclear disaster in Japan in 2011. But the doses are too small to significantly affect humans, plants, livestock or wildlife.

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In the case of nuclear explosions, the downwind range for potentially harmful atmospheric fallout from a 300 kiloton strike in North Korea would be about 160 miles, according to the online tool called NukeMap.

NukeMap allows users to see what would happen in a nuclear attack in any park of the world—just drop a pin to see the potential fallout.

Mankind has already detonated 2,000 nuclear weapons in tests since the 1940's, including 900 in Nevada. The health effects on Americans have been statistically tiny.

Estimates of civilian and military casualties in the opening days of a conflict on the Korean Peninsula range widely, from 30,000 to 300,000 people. At least 136,000 American citizens live in South Korea, including nearly 30,000 U.S. military personnel. Americans would most certainly perish in a second Korean conflict in overseas locales.