Study of Facepiece Leakage of Self-Contained Breathing Apparatus by DOP Man Tests. Progress Report, July 1, 1971--February 29, 1972

摘要

Protection factors (PF's) for Self-Contained Breathing Apparatus (SCBA) have been proposed. The revised B of M Approval Schedules do not have provisions for the determination of protection factors for Self-Contained Breathing Apparatus (SCBA). A protection factor is a measure of the degree of protection afforded by a respiratory protective device during use and is defined as the ratio of the concentration of airborne radioactive material outside the respirator to that inside the facepiece. Protection factors of 10,000 were proposed for a Pressure Demand SCBA and 5,000 for Demand operated SCBA. In April 1971, the H-5 Respirator Research and Development Section began measuring the performance of 30 minute Bureau of Mines approved SCBA to determine the protection factor in the Demand and Pressure Demand Modes. In February, 1972, DOP man tests were completed on all of the 30 minute Bureau of Mines approved SCBA. A total of 540 DOP man tests were performed to provide the data for this evaluation. A protection factor (PF) of 10,000 as proposed for 30 minute Pressure Demand SCBA is quantitatively supported from the DOP Man Test results shown. A demand type of Bureau of Mines approved 30 minute SCBA is limited in regards to protection levels by the facepiece sealing quality on any given individual. Only one of the seven demand type SCBA tested achieved a PF of 500, three achieved a PF of 200, one a PF of 50, and 2 a PF of 20. The demand SCBA are also vulnerable to inward leakage caused by (a) malfunctioning exhalation valves, (b) leaks in the facepiece material and lense seal, and (c) interference of the facepiece seal by facial hair. These factors limit demand type SCBA to those well controlled situations where properly trained and fitted individuals encounter a defined hazard whose upper limits are well within the protection factor provided.