PURPOSE:  Develop certification standards for the approval of self-contained, closed-circuit breathing apparatus used for escape from atmospheres considered to be immediately dangerous to life and health.

RESEARCH SUMMARY:  Closed-Circuit Escape Respirators (CCERs) or Self-Contained Self-Rescuers (SCSRs which is a term used by the mining industry) are used by approximately 50,000 underground mine employees. The overall objective is that no miner should be forced to rely upon an SCSR that might be unsafe for a mine escape. Escape means taking a miner on foot and under oxygen from the deepest point in the mine to a point of safety. A review of the past history of problems encountered with SCSRs during CPIP Investigations reveals that, approximately 40% of the problems involved reliability issues.

Storage of CCERs in harsh environmental conditions, such as heat, cold, and humidity, and the daily wearing of the respirators on and around vibration-generating equipment and tools and during physical work, can result in damage that degrades the respirators’ performance, despite their protective cases. NIOSH field evaluations of certified CCERs conducted systematically and in response to the concerns of users have identified damaged respirators that failed to meet the performance criteria under which they were certified. In some instances, the designs of these respirators, however, did not allow the wearer or employer to evaluate the condition of a particular respirator prior to its use in either an evacuation drill or an actual emergency. Respirator manufacturers have since added design improvements to allow users to check the potential for certain types of damage, but current certification requirements do not specifically govern the inclusion of such checks. Furthermore, current performance testing requirements for CCERs, some of which were established in 1919, rely on a non-uniform testing regime in which differences between human subjects involved in the testing can produce varying test results. The improvements being proposed would establish a consistent testing regimen for evaluating the life support capability of CCERs.

Finally, the current certification requirements are the cause of a risk communication and risk management problem. The requirements compel NIOSH to certify these respirators as providing protection for a specific duration applicable to the particular class of respirator. These durations may be misleading to employers and users, however, because the duration for which one of these respirators will provide effective protection in the workplace, versus in laboratory testing, will depend on the body weight and physical condition of the user and on the amount of exertion required by the escape.

To address the reliability issues involved with the current units, the new standards will incorporate: ruggedness and hazard testing; breathing and metabolic simulator (BMS) testing for capacity, performance, and wearability testing requirements; early detection audits by non-destructive and post certification testing; and voluntary registrations.