Predicting Inward Leakage for Negative Pressure Conditions in a Firefighter Respirator

Published

July 12, 2010

Author(s)

Rodney A. Bryant

Abstract

An analytical model of the flow across a resistive flow path such as an orifice or pipe was applied to predict the inward leakage in an SCBA facepiece during a steady negative facepiece pressure. Starting with a range of negative pressure conditions assembled from the literature, the model was used to estimate leakage rates with respect to the size of the leak. The results of the model were also used to make quantitative estimates of the protection level of the respirator. Experiments were designed to induce a continuous below-ambient pressure inside the facepiece of a pressure-demand SCBA attached to a head form. Negative facepiece pressure measured in the presence of a leak correlated with measured fit factor. The results show that the analytical model generated reasonable estimates of leakage rates during conditions of negative pressure inside the facepiece. Thus the analytical model performed well for constant flow conditions, demonstrating the potential to predict a compromise in respirator protection during negative facepiece pressure conditions.

Proceedings Title

12th International Conference on Fire Science and Engineering

Conference Dates

July 5-7, 2010

Conference Location

Nottingham

Pub Type

Conferences

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Keywords

Respirator, Firefighter, SCBA, Leak, Inward Leakage

Citation

Bryant, R. (2010), Predicting Inward Leakage for Negative Pressure Conditions in a Firefighter Respirator, 12th International Conference on Fire Science and Engineering, Nottingham, -1, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=905693 (Accessed October 10, 2025)