Many manufacturers and other industries have moved away from mercury devices, either out of concerns about the hazards and costs of breakage and cleanups, or because they have found something better.

In case you were to compare the technologies accessible today, he said, “mercury is usually the least correct of all current thermometers in the marketplace. Digital manufacturers have worked very hard to generate products that work to meet the needs of finish users, and usually better.”

“They have become obsolete in various industries as they work to remove them from the measurement stream, and find alternative thermometers,” said Greg Strouse, leader of NIST’s Temperature and Humidity Group.

“We have yet to find an application that they cannot solve with an alternate thermometer,” Strouse said.

For those still using mercury devices, NIST is working with the EPA and private industry to revise over 700 federal product standards that have long necessary the use of mercury thermometers, and find options.

Very? half of those standards already have been amended to permit the use of nonmercury liquids in glass, or digital thermometers using electronic sensors.

They will identify practical alternative thermometers, and write them into the new standards.

The method is expected to take several more years.

The EPA also has proposed new rules that would introduce more such flexibility into both the federal Tidy Air Act and the Poisonous Substances Control Act, where they currently need the use of mercury thermometers.

One of the last and largest challenges for NIST is the petrochemical industry. Natural gas, oil and other fuels expand as they warm up, so temperature measurements are critical to gauging the amount of gas or oil in, or dispensed from, a storage tank. And the industry’s measurement standards long have necessary finely calibrated mercury-in-glass thermometers.