Quantitative respirator fit testing by negative pressure

• Main Author: Murphy, Richard Wright, 1958-
• Other Authors: Crutchfield, Clifton D.
• Language: en_US
• Published: The University of Arizona. 1989
• Subjects: Breathing apparatus > Testing.
• Online Access: http://hdl.handle.net/10150/276947; http://arizona.openrepository.com/arizona/handle/10150/276947

An automated system for quantitative respirator fit testing by negative pressure was evaluated by comparison testing with a computerized aerosol fit test system (Dynatech Frontier Model 260A). The new negative pressure system measures leakage flow while inspiratory pressures are sustained in a respirator facepiece rather than by pressure decay. Four phases of comparison testing were graduated by level of control, ranging from non-subject tests with hypodermic needle leakages to fit tests of 125 Air Force personnel. Throughout the series of tests, negative pressure fit factors were consistently more conservative than aerosol fit factors and showed less variability. Leakage flow rates measured by the negative pressure instrument were highly correlated with leak needle cross-sectional area as predicted by principles of air-flow physics. Comparison of subject and non-subject generated aerosol fit factors indicated significant aerosol losses, possibly due to streamlining and respiratory tract deposition. Negative pressure fit factors were not affected by these subject-related losses.