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Mining Contract: Extending and Monitoring the Scrubber Performance in Escape and Rescue Mining Rebreathers

NOTE: This page is archived for historical purposes and is no longer being maintained or updated.
Contract #12FED1213325
Start Date8/15/2012
End Date4/30/2014
Research Concept

In the event of a mining emergency, self-contained self-rescuers are used for escaping from an underground mine and long-duration closed-circuit breathing apparatus are used in mine search, rescue, and recovery operations. These rebreathing apparatuses consume carbon dioxide chemical absorbents, oxygen-generating chemicals through carbon dioxide absorption, and pure oxygen in a chemical or gaseous form. The performance efficiency of such apparatuses can be optimized by monitoring and/or controlling these consumables.

Topic Area

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to

This contract was funded as part of an interagency agreement program, which provides a formal means for federal government agencies to share and further technology that could apply to and benefit mine safety and health. Through this program, the Office of Mine Safety and Health Research (OMSHR) identifies other government agencies with the knowledge, skills, and abilities relevant to a health and safety gap and works collaboratively with these agencies to identify the type of technology solution desired and to determine specifications for this technology.

Following a catastrophic event, mine workers and rescue teams may be exposed to harmful gases in the mine atmosphere. Breathing air supplies (BAS) technologies are used to isolate the lungs from this atmosphere or provide refuge alternatives where the atmosphere is controlled. Breathing air supplies for underground mining refer to a range of devices and systems that offer respiratory protection to miners in the event of an emergency. Some examples of BAS are self-contained self-rescuers (SCSRs), closed-circuit oxygen breathing apparatus (CCBAs), and gas supplies for refuge alternatives. Advanced BAS technology could improve a mine worker’s chances of surviving a mine disaster.

In the event of a mining emergency, SCSRs are used for escaping from an underground mine and long-duration CCBAs are used in mine search, rescue, and recovery operations. At present, there are no end-of-service life indicators (ELSIs) for the carbon dioxide absorber nor for the oxygen-generating chemicals. The user knows that the apparatus is at the end of its operational life only when the oxygen supply is depleted. Therefore, manufacturers tend to oversize the carbon dioxide absorber in the apparatus design without using the full capacity of these absorbents. On-line monitoring of the carbon dioxide chemical bed would allow the apparatus to be designed more efficiently in relation to its size, weight, and duration.

Under this contract, the Navy Experimental Diving Unit tested three off-the-shelf rebreathers with compressed oxygen supply for actual carbon dioxide scrubber endurance times. These tests involved several different temperatures and workloads and numerous candidate carbon dioxide absorbents. Based on test results, a prototype was built and its function demonstrated. This research also determined the available and emerging technologies for oxygen sensing, specifically suitable for respiratory protective devices in mine applications.