Bellin P, Hinds W C
UCLA Occupational Health Center, Department of Environmental Health Sciences, School of Public Health 90024.
Am Ind Hyg Assoc J. 1990 Oct;51(10):555-60. doi: 10.1080/15298669091370095.
Exhalation valves are a critical component of industrial respirators. They are designed to permit minimal inward leakage of air contaminants during inhalation and provide low resistance during exhalation. Under normal conditions, penetration of aerosol through exhalation valves is minimal. The exhalation valve is, however, a vulnerable component of a respirator and under actual working conditions may become dirty or damaged to the point of causing significant leakage. Aerosol penetration was measured for normal exhalation valves and valves compromised by paint or fine copper wires on the valve seat. Penetration increased with increasing wire diameter. A wire 250 microns in diameter allowed greater than 1% penetration into the mask cavity. Dirt or paint accumulated on the exhalation valve allowed a similar level of penetration. Work rate had little effect on observed penetration. Penetration decreased significantly with increasing aerosol particle size. The amount of material on the valve or valve seat necessary for significant (greater than 0.5%) inward leakage in a half-mask respirator could be readily observed by careful inspection of the exhalation valve and its seat in good lighting conditions.
呼气阀是工业呼吸器的关键部件。其设计目的是在吸气时允许空气污染物的向内泄漏最小化，并在呼气时提供低阻力。在正常情况下，气溶胶透过呼气阀的渗透率极低。然而，呼气阀是呼吸器的一个易损部件，在实际工作条件下可能会变脏或损坏，以至于造成显著泄漏。对正常呼气阀以及阀座上有油漆或细铜线而受损的呼气阀进行了气溶胶渗透率测量。渗透率随线径的增加而升高。直径为250微米的金属丝使进入面罩腔的渗透率大于1%。呼气阀上积聚的污垢或油漆也会导致类似的渗透率水平。工作强度对观察到的渗透率影响不大。随着气溶胶粒径的增大，渗透率显著降低。在良好的光照条件下，仔细检查半面罩呼吸器的呼气阀及其阀座，就可以很容易地观察到导致显著（大于0.5%）向内泄漏所需的阀或阀座上的物质数量。
