The US Mine Safety and Health Administration and the National Institute for Occupational Safety and Health are still conducting a joint investigation into the SCSRs after a group of six tested at Consol Energy’s Enlow Fork mine in southwestern Pennsylvania revealed four malfunctioned units.

“The individual who recorded the test results indicated that one unit expended all of the oxygen upon activation ‘…in a matter of seconds’ [and] he also reported that the other three units did not provide oxygen,” MSHA said.

Another four opened and tested the next day were without problems.

MSHA and NIOSH subsequently tested additional Ocencos at the NIOSH campus and at the mine. Five of six M-20s tested at NIOSH on a simulator functioned properly and a sixth supplied oxygen for eight minutes instead of the required 10 minutes.

“This unit did not malfunction when refilled at Ocenco and tested on a human subject,” the agencies said.

“MSHA and NIOSH continue to analyze the results of the simulator test. With MSHA and NIOSH personnel present at the Enlow Fork mine, the miner who reported the original malfunctions successfully tested three additional M-20 SCSRs.”

MSHA issued an alert on April 19 it would survey operations to determine any problems with units in circulation, and that review revealed that mine operators had tested 275 M-20 SCSRs at 244 mines within the past year as required by MSHA policy.

Of those, four M-20s had issues.

“At one mine, the mine operator reported that two M-20 SCSRs had malfunctioned during testing,” officials said. “However, the miner conducting the tests did not don the units and therefore did not inhale to activate the demand valves.

“At another mine, the mine operator reported that two other M-20 SCSRs had malfunctioned because the miner who performed the tests indicated that the SCSRs did not appear to activate at first. However, both SCSRs worked when the miner breathed into them.”

Ocenco responded to MSHA and NIOSH indicating that it had activated all M-20 SCSRs returned for refurbishment, and had not observed any problems.

Ocenco also tested 12 M-20 SCSRs from units returned for refurbishment with manufacturing dates similar to those reported at Enlow Fork, but none of the units malfunctioned.

“MSHA and NIOSH continue to investigate the issue, but at this time it appears that the reported problems resulted from the manner in which the SCSRs were tested,” the agencies said.

“Accordingly, MSHA and NIOSH have discussed with Ocenco the need to develop and publish procedures for mine operators to use when testing M-20 SCSRs.”

According to federal data, there are about 23,000 Ocenco M-20 SCSRs in inventory across the nation’s mines.

Since 2009, NIOSH has tested 149 M-20 SCSRs from US mines as part of its field testing program, and all of those SCSRs functioned on the simulator.