CHARLESTON, W.Va. -- Federal regulators are working on a plan to phase out the most commonly used emergency breathing device in the coal-mining industry, but have no timeline for getting hundreds of potentially faulty units out of the mines.U.S. Mine Safety and Health Administration officials revealed their intentions Wednesday, just a week after the troubled device's manufacturer -- CSE Corp. -- announced government approval for a new model of self-contained self-rescuer, or SCSR.Neither MSHA nor the National Institute for Occupational Safety and Health has specifically compared the new device with CSE's troubled SR-100 model.Agency officials also have not investigated CSE marketing that promotes the new Self-Rescuer Long Duration, or SRLD, as producing 40 percent more oxygen during the initial start-up and 10 percent more total breathable air."We don't test for that," Jeff Kravitz, MSHA's chief of scientific development, told the Gazette in an interview.Scott Shearer, president of Monroeville, Pa.-based CSE Corp., did not return a phone call. In a press release last week, Shearer called approval of his company's new device "a tremendously important step for the continued improvement of safety and support for miners.""The quality of the new SRLD is unmatched and once in the field to our customers, the SRLD will be the smallest, lightest, fastest working unit available in its class," Shearer said in the release.CSE said the new SRLD also includes new indicators to warn of damage from water vapor or temperature."This product is designed with both miner safety and miner convenience in mind and we have pulled out all the stops," Shearer said. "We look forward to manufacturing this device and getting it to our customers who are equally as excited."Under federal law, all coal miners must be provided with a self-rescue device that will provide them with at least an hour's worth of breathable air to escape in the event of an underground fire or explosion.The SR-100 model uses a chemical process to generate oxygen, based in part on a reaction with carbon dioxide being exhaled by its user. An estimated 70,000 SR-100 units -- and perhaps as many as 90,000 -- are in use in coal mines across the country.SCSRs received new public attention five years ago, after Sago Mine Disaster survivor Randal McCloy testified that the SCSRs of four of the 12 miners trapped by the Jan. 2, 2006, explosion wouldn't start.Over the years, coal miners had expressed similar complaints about SCSRs not starting or appearing to start slowly. Government and industry officials have generally dismissed those complaints. They said the problem was that miners weren't properly trained or didn't understand how their SCSRs worked.Then last year, MSHA and NIOSH launched a joint investigation of problems that were eventually traced to the oxygen cylinders used in the initial start-up of the SR-100 devices. Initially, CSE said it had instituted a "recall" of the troubled units, but later conceded it had not actually ordered coal companies to stop using the devices.In lawsuits after the Sago disaster, families of the miners were investigating concerns that the SR-100 cylinders -- made by a South African company -- somehow leaked, leaving the units without enough oxygen to start properly. Those suits were settled, and the terms were kept confidential.Kravitz said the new CSE device uses different oxygen cylinder and starter components that don't involve the threaded connections that could have been the problem with the SR-100. "We definitely think that is going to fix the problem," he said.Roland BerryAnn, deputy director of the NIOSH lab that reviewed the new device, said his staff did not do a direct comparison with the SR-100 because CSE submitted an application for a new product, rather than changes to its existing devices."If the new unit had been as an action to correct the identified problem, we would have done a comparative to see how the problem was corrected," BerryAnn said earlier this week.BerryAnn also said NIOSH does not test breathing devices to see how long they will last, but only to ensure that they will meet the 60-minute requirement in federal law.In a notice dated July 29, but not made public until Wednesday, NIOSH said it had determined a potential failure rate of the SR-100's oxygen starter cylinders of between 1.25 percent and 2 percent -- meaning as many as 1,400 faulty units could be in use.MSHA doesn't know how long it will take to phase out the SR-100s. "We think we're going to have to work that out with NIOSH," Kravitz said.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.