"I was in a mine in New Mexico about three weeks ago that had a refuge area,'' said Main, who worked for decades underground without such a fallback. "Refuge chambers are now commonplace.''

The same is true of the oxygen generators that miners wear on their belts.

"Prior to the Sago disaster you had about one apiece,'' Main said. "Now you have multiple devices available.''

The legislation also required family liaisons to work with the families of miners killed in major disasters. Main has assigned a liaison for every fatal accident. "We owe it to the families,'' he said.

Sen. Jay Rockefeller credited the MINER Act with reducing coal mine fatalities 14 percent and injuries 25 percent.

"The MINER Act was a huge step forward. Safety laws save lives and keep families intact,'' the West Virginia Democrat said.

Rockefeller, however, renewed calls for more legislation to protect miners.

"It's not enough,'' he said. "We know from the terrible tragedy at Upper Big Branch that we must do more.''

An explosion killed 29 miners at Upper Big Branch on April 5, 2010. The tragedy was the deadliest at a U.S. coal mine since 1970. It sparked state and federal civil investigations and a federal criminal probe, but little legislation.

"We have said that we think that there is a need following Upper Big Branch, with all we know, is to move forward with legislation,'' Main said.

Whether the mandate will immediately improve safety for the nation's 46,000 underground coal miners is unknown because it's uncertain how many mines installed everything they needed in time.

The most recent numbers from the federal Mine Safety and Health Administration show that as of April, 64 percent hadn't fully installed the required wireless equipment.

The equipment had better be there, MSHA Director Joe Main told The Associated Press.

"We're going to find out,'' Main said. "Mines are obligated to have their communications systems in and we're going to be applying the strength of the Mine Act.''

Main offered few specifics, saying only that communications and tracking equipment will be checked during regular inspections.

The deadline coincides with the fifth anniversary of landmark mine safety legislation passed after 12 miners died at the Sago Mine in Upshur County, followed by two more miners at the Aracoma Mine in Logan County, and five more at the Upper Darby Mine in Kentucky.

Some violations are likely to occur, in part because some are using technology that didn't exist in 2006 and only recently received approval for underground use, Main said.

"I will temper what I'm saying with this: We know that this is new technology, some of it just came through the pipelines in the last few months,'' he said. "There's going to be glitches.''

The National Mining Association estimates that companies have since spent $1 billion complying with the law.

The final piece is communications and tracking. Other requirements were completed long ago.

Mines, for instance, now must store two hours of breathable air per miner every 30 minutes along escape routes. They also must have airtight refuges capable of keeping trapped miners alive for 96 hours. The law also beefed up training requirements for mine rescue teams and miners and required mines to report accidents within 15 minutes. The number of rescue teams trained to enter mines and find and help miners has increased nearly 50 percent, Main said.

"I was in a mine in New Mexico about three weeks ago that had a refuge area,'' said Main, who worked for decades underground without such a fallback. "Refuge chambers are now commonplace.''

The same is true of the oxygen generators that miners wear on their belts.

"Prior to the Sago disaster you had about one apiece,'' Main said. "Now you have multiple devices available.''

The legislation also required family liaisons to work with the families of miners killed in major disasters. Main has assigned a liaison for every fatal accident. "We owe it to the families,'' he said.

Sen. Jay Rockefeller credited the MINER Act with reducing coal mine fatalities 14 percent and injuries 25 percent.

"The MINER Act was a huge step forward. Safety laws save lives and keep families intact,'' the West Virginia Democrat said.

Rockefeller, however, renewed calls for more legislation to protect miners.

"It's not enough,'' he said. "We know from the terrible tragedy at Upper Big Branch that we must do more.''

An explosion killed 29 miners at Upper Big Branch on April 5, 2010. The tragedy was the deadliest at a U.S. coal mine since 1970. It sparked state and federal civil investigations and a federal criminal probe, but little legislation.

"We have said that we think that there is a need following Upper Big Branch, with all we know, is to move forward with legislation,'' Main said.