The devices -- developed by Axcess International Inc., a manufacturer of wireless monitoring products, and Tunnel Radio of America Inc. -- are designed to track the location of individual miners in order to aid rescue operations in case of an accident. The tags transmit in the 315 to 433 MHz band, which Allan Griebenow, president and CEO of Axcess International, said is more robust than Wi-Fi transmitting at 2.4 GHz.
"The tag is connected directly to the side of the helmet, and it technically can be worn in the pocket or even provided around a lanyard as an ID," Griebenow said.
The safety rule, effective mid-year 2009, was prompted by the tragic Sago mine disaster in Upshur County, W. Va., on June 2, 2006. Twelve miners suffocated there after being trapped by an underground explosion. Investigators faulted the slow rescue effort, miscommunication -- family members of the killed miners were mistakenly told they were alive -- and first responders' inability to notify the trapped miners that a rescue attempt was under way.
In the wake of that tragedy, President George W. Bush signed The Mine Improvement and New Emergency Response Act, which amended the 1977 Mine Safety and Health Act to require that mine operators implement post-accident rescue plans and provide their miners with wireless tracking systems, among other improvements.
"I think what's been interesting about this three-year period [since then] is it's taken that amount of time to get the combination of robust trunking technologies and robust tagging technologies to work together to be able to provide a solution that's reliable and cost effective," Griebenow said.
"You must have tags that are sealed; our tags will actually transmit out of a glass of water if you want them to," he said. "I think it's also important to note that the trunking backbone in a mine is unique. You can't just drop a typical Wi-Fi transmitter and access point in a mineshaft because you have various level changes and obstacles."
The tags automatically page third parties, such as first responders, when miners trigger an alert, Griebenow said. In the case of an emergency, first responders can use software to determine the workers' location on a mine diagram.
In the future, Axcess might be able to expand the tag's features to include measurements such as ambient temperature and motion sensing, he said.
The MSHA has approved 45 tracking and communications products so far that meet the standard, and more applications for approval are in the pipeline. The MSHA groups these devices into categories:
- handheld two-way radios
- mine page phones, which are "self-contained, battery-powered communication units that provide loudspeaker paging and handset party line conversation over a two-conductor telephone line"
- leaky feeder communication systems -- "two-way radio systems that feature a base station on the surface that communicates with individual underground radio units, such as walkie-talkie radios" via a cable network
- radio frequency identification (RFID)
- personal emergency devices (PED), which are a "belt-wearable receiving units for individual miners" that can receive text messages.
