8 'notifications' in a decade In the past 10 years, the National Institute of Occupational Safety and Health has issued eight "notifications to users" regarding problems with emergency breathing devices -- self-contained self-rescuers -- used by miners. Nov. 14, 1997 -- MSA Portal-Pack Chemical fragments and fine particles were found in some units' breathing tubes. The chemical dust, if inhaled, could cause choking. All Portal-Packs were recalled and replaced with MSA Life-Saver 60s. Aug. 11, 1998 -- Ocenco EBA 6.5 Some SCSRs produced or factory serviced from June 1, 1997, through March 31, 1998, were equipped with unapproved exhalation valves. Tests showed breathing was more difficult. Devices were refurbished or replaced as quickly as possible. Dec. 22, 1999 -- CSE SR-100 A miner in a Dec. 8, 1999, mine fire suffered smoke inhalation because his SCSR had a deteriorated breathing tube. An investigation showed that SCSRs manufactured prior to June 7, 1994, had rubber tubes; those made later were of silicon. SCSRs with rubber tubes were recalled and removed from service. June 27, 2000 -- Draeger OxyK-Plus Various amounts of potassium superoxide were found outside the chemical cartridge in some of the units. In some instances, it had infiltrated the breathing circuit and could be exposed to the user. Miners were instructed to check these units and, if dust was seen, return them to the manufacturer. Oct. 4, 2001 -- Draeger OxyK-Plus 561 SCSRs delivered to mines in North America were found to have improperly assembled breathing bag relief valves. Miners were told to check the serial numbers of their units and remove affected ones from use. March 4, 2002 -- MSA Life-Saver 60 Signs of potassium superoxide were observed in the mouthpiece of one unit and detected in the breathing tubes of five others. Miners were told to look for dust before using. Also, the company recommended recalculating the service life of the devices so that they would be taken out of service more quickly. Nov. 5, 2002 -- Ocenco EBA 6.5 SCSR Deteriorated breathing hoses were found on some units manufactured or refurbished in 1992. These SCSRs were no longer "in approved condition." Models made in that year and in the first three months of 1993 were recommended for recall. Nov. 14, 2002 -- MSA Life-Saver 60 Part of the devices on units made from October 2000 to July 2000 could become excessively hot because of too much iron powder. The units involved were removed from use.

The poisonous gases in a Kentucky coal mine where five miners died Saturday have finally cleared. What isn't clear is whether the emergency breathing devices the miners carried with them worked properly. And, if not, why?

Three of the miners who died Saturday at Darby Mine No. 1 survived the initial blast only to be overcome by carbon monoxide. Another miner, Paul Ledford, who survived, told his brother that the air pack he used to escape worked for only five minutes.

However, David G. Dye, acting administrator of the federal Mine Safety and Health Administration, has said in a statement that Mr. Ledford's air pack worked properly.

It's the kind of discrepancy that has frustrated miners and their families and sparked government investigations.

The men who died of carbon monoxide poisoning in Kentucky were using the same make and model air pack -- called a self-contained self-rescuer -- as the Sago Mine disaster victims in West Virginia. The lone survivor of Sago, Randal McCloy Jr., has said that some of the SCSRs his co-workers carried did not work.

"Since January, 14 miners have died and one, my husband Randy, suffered a severe brain injury as a direct result of carbon monoxide poisoning in the mines," Anna McCloy said in a statement released yesterday from her home in Simpson, W.Va. "Report after report has shown the rescuers did not work like they are supposed to. ... Why?"

Investigators with the Mine Safety and Health Administration have checked the SCSRs carried by the Sago miners and said that the units appear to have been activated and should have worked. The units have been forwarded to a National Institute for Occupational Safety and Health laboratory for additional testing.

These aren't the first instances when NIOSH has been called in to check miners' SCSRs. In the last 10 years, there have been nearly three dozen investigations into complaints concerning air packs.

According to NIOSH spokesman Fred Blosser in Washington, D.C., only eight of those reviews resulted in recalls or replacement of the SCSRs involved.

The eight complaints that brought about recalls or replacements affected all four companies that manufactured SCSRs: Ocenco; Draeger; CSE; and MSA. MSA, which is based in Pittsburgh, stands for Mine Safety Appliances, but MSA spokesman Mark Deasy yesterday said the company stopped making SCSRs in 2004 and shipped its last batch out in January 2005.

MSA got out of the SCSR business, he said, not because of trouble making the units but because another company, Monroeville-based CSE, dominated the market to the point that it was not profitable for MSA.

CSE is the maker of the SR-100 units used at the Sago and Darby mines.

Mr. Blosser said most of the units tested by NIOSH are done the request of the user.

"That's part of our mission, and we've been doing this for years," he said. "The Sago investigation is a different animal because it was something MSHA requested us to do specifically.

"The process is that we will give [our] report to MSHA and the information will become part of their record of the investigation."

Mrs. McCloy is one of those waiting for the investigation to reach its next step.

"MSHA and various company officials continue to say the rescuers were tested and had operated properly," she said in her statement. "This doesn't add up."

Mr. Blosser expressed sympathy for Mrs. McCloy and everyone else demanding answers.

"It's understandable," he said. "People are concerned.

"If these devices are regarded with some degree of uncertainty, we want to do what we can to help provide answers."