日本核危机发生以来，美国各地的辐射侦测器销量大增，很多销售点的存货都已受控，新货订单都排到了几周以后。

Since Japan’s nuclear crisis started, Tim Flanegin’s phone has barely stopped ringing with orders for Geiger counters, the radiation detectors², to the point that（到……程度） he has no more in stock.

With small amounts of radiation from Japan’s damaged reactors³ wafting⁴（飘荡，吹拂） across the Pacific Ocean, relief crews, businesses and ordinary consumers have bought nearly every Geiger counter available from the few retailers⁵ that sell them. The run is a grim reminder⁶ of the scope of the disaster and the widespread concern about radiation contamination, including in the United States.

Many people buying the devices say they are worried about their food becoming contaminated. One customer, Mr. Flanegin said, was a theme park in Japan that wanted to check its food supplies as a precaution for its visitors.

Radiation detectors come as hand-held devices, wrist watches and pager-size gadgets⁷ that hang from the belt. Their cost varies from $150 for a self-assembled kit⁸ to $4,000 for a more sophisticated version that stores radiation readings along with the GPS coordinates⁹ of where those readings were taken.

Technically¹⁰, Geiger counters are just one type of radiation detector¹. But many people use the term to describe all radiation detection equipment.

Law enforcement, fire departments, military, hospitals, scientific laboratories, schools and prospectors¹¹ are the typical customers. Federal government agencies seem to be well enough stocked that they are not scrambling¹² to buy more, according to the sellers interviewed.

Usually, the general public, other than a small group of hobbyists, has little interest in radiation.

But that changed after a devastating¹³ earthquake and tsunami¹⁴ set off Japan’s nuclear troubles. Demand for radiation detectors, along with potassium iodide pills, which can help prevent radiation-induced thyroid（甲状腺） cancer, quickly outstripped¹⁵ supplies and the limited capacity to produce more.

Skepticism that the government will be forthcoming about radiation levels is driving some of the sales, said John Iovine, president of Images SI, a company in Staten Island that makes and sells Geiger counters and other scientific instruments.

“I never really felt it until people started calling up,” he said. “They want their own Geiger counter to check up.” Radiation levels in the United States remain within the normal range, according to the Environmental Protection Agency, which has a network of monitors across the country. Updates are available on the E.P.A.’s Web site.

During a typical week, Mr. Iovine says, he may get an order for 20 Geiger counters from a local government followed by several weeks without any additional sales. But in the week after the Japan earthquake, he said he received close to 200 orders and was now sold out. Customers are now warned that it will take six to eight weeks to fill any orders.

Still, buying a radiation detector is just the first step, Mr. Iovine said. Owners of the devices need to discern between dangerous radiation levels and a normal background reading.

“To use it is very simple,” Mr. Iovine said. “To interpret the results gets a little more difficult.”

Naturally occurring radiation varies depending on factors like local geology and altitude. People are exposed to additional radiation when they get an X-ray or fly in an airplane.

Robert Corsetti, director of sales and marketing¹⁶ for Berkeley Nucleonics, which makes and sells industrial-grade radiation detection equipment, said that calls to his company, which is based in San Rafael, Calif., increased up to 15 times the normal level after the problems started in Japan. In some cases, people are simply calling to ask if they are at risk, and not to buy something.