Date of Graduation

2000

Document Type

Thesis

Degree Type

MS

Committee Chair

Mridul Gautam

Abstract

Air is known to contain a variety of airborne matter that is considered as potential health hazards. These particles if ingested/inhaled have long term effects on the health of human beings. The best technique to prevent these harmful particles from reaching the respiratory tract is physical interception. Personal protective equipment such as respiratory filters are used extensively to administer clean air of exceptional quality. The objective of this study was to evaluate the performance of commercially available respirator filters subjected to extremely heavy loading conditions. Several commercially available brands of P-100 and P-95 particulate filters were tested. The test conditions were maintained in accordance with the requirements of 42 CFR part 84 that addresses particulate respirator certification. The only alteration from the 42 CFR 84 specifications was that the filter classes were subjected to Di-Octyl Phthalate (DOP) aerosols of the most penetrating particle size (CMD of 0.17  0.01 m and a GSD of 1.6  0.1), till approximately 1000  5 mg of DOP contacted the filtering surface. At a challenge concentration of 80 mg/m3 and an air flow rate of 85  2.5 LPM test duration was approximately 150 minutes. The filter penetration and pressure drop characteristics were measured instantaneously using the Automated Filter Tester (AFT) model 8110 manufactured by TSI. A Quality Factor (QF) as proposed by Brown (1993) was evaluated for each brand of filter. The QF can be used as an effective reference to evaluate the performance of various types of particulate filters at different stages of loading, and depending on a standard value of QF the service life of the filters can be clearly defined. In addition, particle size of the aerosol penetrating the filter was monitored at distinct loading levels for each brand of filters. A combination of Scanning Mobility Particle Sizer (SMPS) and Condensation Particle Counter (CPC) was used for this study. Statistical analysis of the data was performed to get clues on the presence of wicking phenomena. The aerosol particles coming off the filter were compared with the raw challenge aerosol and the aerosol particles penetrating at initial loading conditions (20 mg DOP loading). The results revealed that the pressure drop increased as the amount of loading increased for all the filters tested. The P-100 filters had low initial penetration and high resistance to air flow (high pressure drop). With an increase in loading, the penetration decreased to a minimum, further loading resulted in an increase in the penetration towards the end of the test. The P-95 brands had higher penetration at the beginning of the tests, it decreased with further loading and remained constant over a period of time. At excessive loading conditions a slight increase in the percent penetration was observed. The particle sizing study indicated the presence of wicking at higher loading conditions.

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