Charles Dharapak, Associated Press With Sago Mine survivor Randal McCloy Jr. and his wife, Anna, sitting in front, President Bush reaches out to shake hands with Sen. Patty Murray, D-Wash., after he signed the MINER Act yesterday. Click photo for larger image. Full text of President Bush's remarks

Flanked by family members of coal miners killed in an unusually deadly year underground, President Bush yesterday signed into law the MINER, or Mine Improvement and New Emergency Response, Act -- a bill that has experts unsure what impact it will have on an industry facing intense demands to improve its safety record.

The new law sets a 15-minute time limit for reporting serious accidents, doubles the required amount of emergency oxygen supplies and increases fines for safety violations.

Yet critics point out that it fails to incorporate more stringent requirements initially sought by mine-state legislators -- such as underground rescue shelters and a strict deadline for upgraded communications -- and that it does little to prevent disasters in the first place.

One major ambiguity is whether the law eliminates an old six-point assessment system that has previously allowed judges at the Mine Safety and Health Review Commission to drastically reduce fines.

Mr. Bush, in an emotional White House ceremony that included families of the 12 men killed in the Jan. 2 Sago Mine disaster and the lone survivor, Randal McCloy Jr., extolled the bill.

"The MINER Act will build on the Mine Safety and Health Administration's ongoing efforts to enhance mine safety training, to improve safety and communications technology for miners and provide more emergency supplies of breathable air along escape routes," the president said.

As Mr. Bush put his signature to the law, U.S. Rep. George Miller, a ranking Democrat on the House committee that oversees workplace safety, was reiterating his doubts.

Mr. Miller, D-California, had tried to stall the bill in the House when the chamber failed to accept amendments tightening deadlines and making oxygen requirements more strict.

"I'm worried that the pressure to do something now is relieved by the passage and signing of this bill, and I think this is still a very urgent matter," Mr. Miller said.

He wanted underground tracking systems for miners within 15 months rather than the three years called for in the final bill, and a mandatory two-day supply of oxygen for trapped miners, rather than the two hours finally called for in the law. He also wanted spot-checks of emergency breathing devices.

The new bill does raise many minimum fines for safety violations, from $60 to $2,000, and $4,000 in some cases, with "flagrant" safety violations jumping to a maximum of $220,000.

That assumes the law eliminates the formula used by appeals judges to decide whether to reduce fines, but it contains no specific language on that point. This raises the specter that the new numbers could prove meaningless.

Ed Clair, chief counsel for MSHA, said yesterday that the $2,000 and $4,000 fines for violations are minimums that administrative law judges cannot reduce.

But Michael F. Duffy, chairman of the review commission, said he believes the courts will be asked to settle the question.

"It'll have to be resolved under litigation," Mr. Duffy said yesterday.

The new law carries a few mandatory requirements:

Each miner must have two hours of emergency oxygen available at work sites, and caches of air supplies must be placed along escape routes.

Mines must regularly update rescue plans, and underground rescue teams must be within an hour's travel time.

MSHA now can seek court injunctions to shut down mines whose owners ignore outstanding fines.

Less specific language on other matters leaves a great deal up to the secretary of labor and MSHA, something that worries administration critics.

"One of them is belt air, which is a big issue for us," said Phil Smith, a spokesman for the United Mine Workers of America.

Belt air -- a relatively new MSHA rule allows mine operators to run fresh intake air to miners through the same corridors where conveyor belts move coal -- has been a flash point in the industry since Jan. 19.

On that date, a belt in an air intake corridor caught fire at the Aracoma Coal Co.'s Alma No. 1 mine in Logan County, W.Va., sending a cloud of smoke into the work area. Two miners died of smoke inhalation. The mine, owned by Massey Energy Corp., is now the subject of a criminal investigation over its handling of the incident.

"If you look at Aracoma, if belt air hadn't been allowed to be used, those guys would have lived," said Dennis O'Dell, director of safety for the UMW.

The law signed yesterday establishes a "technical panel" on belt air to revisit the question.

"It just says they'll look at that," Mr. Smith said. "That's obviously one of the bigger things we're concerned about."

The law also calls for MSHA to develop new standards for sealing abandoned areas of mines. A wall blew out when methane ignited in an old work site at Sago Mine No. 1 in Upshur County, W.Va., touching off the Jan. 2 disaster. Later investigation showed that the wall, constructed of lightweight Omega block, easily gave way, raising questions about how the blocks were installed and about the standard for how much pressure they should be able to withstand.

The current U.S. standard is 20 pounds per square inch, compared with 50 psi or more in some other countries. The new law calls for an increase from 20 psi, but leaves it up to MSHA to set the new minimum.

Bruce Watzman, vice president for health and safety at the National Mining Association, an industry group, said many of the goals sought in the new law are, at least at present, impractical.

Speaking earlier this week before the National Coal Show in Pittsburgh, Mr. Watzman said the requirement that MSHA make wireless communications available underground within the next 15 months assumes the technology will be available. He also said belt air is sometimes necessary to lower methane levels underground.

"Belt air is used for a whole host of reasons," he said.

However MSHA chooses to interpret the new law, it will do so, at least for a while, without a permanent leader. Senate Majority Leader Bill Frist, R-Tenn., yesterday canceled a vote on the confirmation of Richard Stickler as head of MSHA. Mr. Stickler has been criticized by congressional Democrats and UMW officials for being too sympathetic to the coal companies he would be asked to regulate.

Mr. Bush put in a strong plug for Mr. Stickler at yesterday's signing ceremony.

"He's got experience. He served for six years as the director of Pennsylvania's Bureau of Deep Mine Safety. He was a miner, mine shift foreman, a superintendent and a manager, and the Senate needs to confirm Richard Stickler to this key position," Mr. Bush said.

Debbie Hamner and Sara Bailey, the wife and the daughter of the late Sago miner George Junior Hamner, sent a letter to Mr. Bush yesterday thanking him for signing the MINER Act but strongly urging him to withdraw Mr. Stickler's nomination.

Noting Mr. Stickler's long experience in coal mine management, they wrote: "We are concerned that his primary objective may be 'compliance assistance' and production, rather than on miners' health and safety."

They said Mr. Stickler "declined to endorse new mine safety rules" at his nomination hearing, including ones that would have required improved emergency oxygen equipment. Mr. McCloy, the Sago survivor, has said that four of his crew's oxygen packs did not work.

"Our nation's miners deserve an agency staffed with leaders who will aggressively advocate miners' health and safety," wrote Mrs. Hamner and Ms. Bailey. "We assert that Mr. Stickler is not the right person for the job and urge you to withdraw his nomination."