Honors College Theses

Publication Date

4-12-2018

Major

Mechanical Engineering (B.S.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dr. Aniruddha Mitra

Abstract

This experimental investigation studies the effectiveness of N95 respirators at blocking particles between 11.5 and 154 nm in diameter during 4 different construction activities. It is well known that large amounts of dust and debris are generated during construction activities. New research has found that significantly more nanoparticles are generated during construction activities than previously thought. Consequently, the N95 respirators commonly worn to protect against these particles are only rated to block 95% particles larger than 0.3 microns in size. In this investigation, two respirator models were tested, a NIOSH TC-84A-0007 pleated N95 respirator and a NIOSH 42CFR84 foldable N95 respirator. The effectiveness of the respirators was evaluated by measuring the percent penetration of particles through the mask. A testing apparatus was developed to evaluate these respirators in the field, under real world conditions. The construction activities measured were concrete grinding, concrete mixing, earth moving, and wood framing. The average percent penetration of particles through the respirators across all 4 construction activities was found to be 5.99%. Comparing the two respirator types, it was found that the percent penetration for the pleated respirator was 6.27% more than the foldable respirator on average. While the respirators were effective at blocking particles smaller than 27.4 nm, they were less effective at blocking particles between 27.4 and 154 nm, having percent penetrations greater than the mask’s 5% penetration rating. Therefore, while the real time filtration efficiency of N95 respirators against nanoparticles was often greater than 95%, efficiency for nano-sized particles was inversely proportional to size for particles less than 27.4 nm.

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