Effect of Respirator Resistance on Tolerant Capacity during Graded Load Exercise

Respirator breathing resistance impacts performance of wearers during constant work load. However, it is less clear as to how breathing resistance affects the tolerant capacity of users during graded work load. The present study investigated the tolerant capacity of 8 individuals during incremental work load. The 8 subjects were required to wear two matched respirators （respirators Ⅰ and Ⅱ which were designed to have different breathing resistances and the same dead space） respectively on separate days and then work to end points. Minute ventilation （VE）, breathing frequency （BF）, oxygen consumption （VO2） and heart rate （HR） were recorded during exercise, while tolerant time, response time and breathing discomfort were measured at the end of each test trial. The test variables were com-pared between the two respirators by using matched-pairs t-test. The results showed that the tolerant time was significantly reduced for the respiratorⅠwith higher level of breathing resistance when compared with its counterpart with lower breathing resistance （respirator Ⅱ） （P〈0.05）. The same changes occurred for response time. Results also showed a significant increase in VE and BF for respirator Ⅰwearers when the work load was above 125 W. The O2 consumption was similar under the two breathing resistance conditions. These findings suggested that the respiratory resistance caused by self-contained breathing apparatus （SCBA） has an impact on the tolerant capacity of users.

Performance of N95 elastomeric respirators in high humidity and high coal dust concentration environment

High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study investigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased(minimum value 97.5%).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa^(-1).As the PM2.5 coal dust concentration increased from 5 to 50 mg/m^(3),the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.