Determination of Known Exhalation Valve Damage Using a Negative Pressure User Seal Check Method on Full Face Respirators Lisa J. Delaney, M.S., NIOSH Roy T. McKay, Ph. D., University of Cincinnati Andrew Freeman, M.D., University of Cincinnati

Respirator Leakage Pathways Improper respirator-to-face seal Inefficient air filtration device Leak sites in the respirator body Improperly functioning exhalation valves Source: Brueck, Scott et.al. Method Development for Measuring Respirator Exhalation Valve Leakage. Am.Ind. Hyg. Assoc. 7(3): (1992).

Exhalation Valves Consists of valve seat, valve, and valve cover Allows for unidirectional airflow out of respirator Prevents unfiltered air from entering respirator

Regulations and Recommendations OSHA NIOSH ANSI

Negative Pressure User Seal Check (NPUSC) Procedure –Cover filter/cartridge opening with palm of hand, –Inspire as to create a negative pressure to cause the respirator to collapse slightly, and –Hold breath for a designated amount of time Criteria for Passing –Facepiece remains slightly collapsed AND –No inward air leakage is detected

Respirator Leak Checker™ Measurement device developed by Drs. Freeman and McKay, Univ. of Cincinnati Measures in-mask pressure differentials Assesses ability of respirator wearers to properly conduct a USC

Hypotheses 1.Test subjects can identify respirator leakage due to damaged exhalation valves by performing NPUSCs. 2. The RLC can detect respirator leakage due to damaged exhalation valves.

Materials Full facepiece elastomeric respirator with oral/nasal cup Exhalation Valves 1.Undamaged (control) 2.Warped 3.Slit 4.Adhesive

Materials con’t. Ambient aerosol (AA) condensation nuclei counter- T.S.I. PortaCount Plus  Controlled negative pressure (CNP)- Dynatech Nevada 3000  In-mask pressure differential- Respirator Leak Checker

Test Protocol Respirator size selected and donned Test subject trained The following tests were performed for each valve (beginning and ending with the control exhalation valve): –NPUSC –RLC measurement –TSI PortaCount measurement –Dynatech Nevada Fit Tester 3000 measurement

Select and don respirator Perform NPUSC and obtain RLC measurement Perform PortaCount fit test Perform Dynatech Nevada fit test Replace with next exhalation valve? NoYes Stop

Modifications from OSHA Protocol NPUSC –Held breath for 7 seconds instead of the OSHA required 10 seconds TSI PortaCount –Test subject remained facing straight ahead during all measurements –Fit factor calculated from third maneuver

Modifications from OSHA Protocol con’t. Dynatech Nevada Fit Tester 3000 –Fit factor calculated from first maneuver, normal breathing, head facing straight ahead

Data Analysis Fit factors analyzed using a repeated measure analysis of variance (ANOVA) to determine differences between valves Maximum pressure generated and time above threshold during NPUSC were analyzed using ANOVA to determine differences between valves

Test Subject Characteristics 26 test subjects included in study 54% male/46% female 50% were experienced respirator wearers

Relationship Between Fit Factors and Percent Failing/Unsure NPUSCs

In-Mask Pressure Differential Measurements During NPUSC 98% (102/104) met the criteria set for passing the NPUSC Failed tests occurred with the undamaged and slit valves No significant difference between maximum pressure generated and time above threshold between the damaged and undamaged valves

Conclusions NPUSCs rarely identified leakage due to exhalation valve damage RLC was useful for assessing ability to conduct NPUSC Inspection, fit testing, and NPUSC is needed to maintain proper protection

Acknowledgements Support for this research was received in part through the NIOSH ERC Grant to the University of Cincinnati (T42 CCT510420) and from the University of Cincinnati Dr. Roy McKay