Campbell D L, Noonan G P, Merinar T R, Stobbe J A
National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505-2888.
Am Ind Hyg Assoc J. 1994 Apr;55(4):322-9. doi: 10.1080/15428119491018961.
An analytical model is presented that estimates the distribution of workplace protection factor (WPF) values for positive-pressure respirators. Input for the model is (1) the instantaneous facepiece pressure measured as a function of time and (2) the distribution of WPF values for a negative-pressure version of the respirator. As an example application, the model was applied to 57 measurements of facepiece pressure made in a previous National Institute for Occupational Safety and Health study called "Firesmoke." That study involved professional firefighters wearing positive-pressure self-contained breathing apparatus (SCBA). During Firesmoke, there were four donnings in which facepiece pressure momentarily went negative one or more times during use. The purpose of the effort described here was to assess the significance of these momentary, negative excursions in facepiece pressure. To that end, an analytical model was developed that estimates the ratio of the mass of contaminant that enters the facepiece during these negative excursions to that which would be expected to enter a negative-pressure respirator utilizing the same facepiece. Thus, the performance of a positive-pressure SCBA can be determined relative to the performance of a negative-pressure respirator with the same facepiece--either a negative-pressure SCBA or a negative pressure air-purifying respirator. The NIOSH-assigned protection factor (APF) for a negative-pressure full facepiece is 50; the APF for a positive-pressure SCBA is 10,000. The results of the application of this analytical model are consistent with the current NIOSH APF for a positive-pressure SCBA.
本文提出了一种分析模型，用于估计正压呼吸器的工作场所防护因数（WPF）值的分布。该模型的输入为：（1）作为时间函数测量的面罩瞬时压力；（2）该呼吸器负压版本的WPF值分布。作为一个示例应用，该模型被应用于美国国家职业安全与健康研究所先前一项名为“火灾烟雾”研究中的57次面罩压力测量。该研究涉及佩戴正压自给式呼吸器（SCBA）的职业消防员。在“火灾烟雾”研究期间，有四次佩戴过程中，面罩压力在使用过程中瞬间出现一次或多次负压情况。此处所述工作的目的是评估面罩压力这些瞬间负压波动的重要性。为此，开发了一种分析模型，用于估计在这些负压波动期间进入面罩的污染物质量与预期进入使用相同面罩的负压呼吸器的污染物质量之比。因此，可以相对于具有相同面罩的负压呼吸器（负压SCBA或负压空气净化呼吸器）的性能来确定正压SCBA的性能。负压全面罩的美国国家职业安全与健康研究所指定防护因数（APF）为50；正压SCBA的APF为10,000。该分析模型的应用结果与美国国家职业安全与健康研究所目前对正压SCBA的APF一致。
