Federal regulators are concerned the defect could affect 70,000 to 90,000 self-contained self rescuers in use by miners across the nation's coalfields, according to Les Boord, director of personal protective technology at the National Institute for Occupational Safety and Health.
"We think it's a problem," Boord said in a phone interview Tuesday.
Earlier Tuesday, the U.S. Mine Safety and Health Administration disclosed a "user notice" in which CSE itself acknowledged the potentially broader scope of problems with its SR-100 model.
"Until the root cause can be identified, we must assume that the potential for start-up oxygen cylinders to fail may extend to any field-deployed unit, and not just the serial numbers that were previously identified," CSE said in the notice, dated Monday.
In late February, Monroeville, Pa.-based CSE announced what it said at the time was a "recall" of more than 4,000 units because of concerns about the oxygen starter mechanism.
But contrary to the company's press release, CSE has not actually recalled any of the potentially affected units. None have been taken out of service or replaced, company president Scott Shearer said in an interview.
Instead, CSE is warning miners that the units might not start initially and urging mine operators to update training on a backup manual startup procedure.
"If for any reason a unit does not inflate the breathing bag, the user should don another unit if one is readily available," CSE said in a user notice issued Monday. "If a second unit is not readily available, the manual start should be used."
CSE had originally said in February that it believed the oxygen starter problem involved only a small portion of one lot of 4,000 SR-100s manufactured in May 2009.
The company said Tuesday its concerns had expanded to two lots and involved as many as 11,000 units. "We feel it is a very small part of the population, but we've taken the added precaution to alert everybody," Shearer said.
But NIOSH officials revealed that their agency and CSE had been jointly investigating similar oxygen starter problems with previously manufactured SR-100s since December -- two months before the company's February announcement.