Investigation of potential affecting factors on performance of N95 respirator

Document Type

Journal Article

Publication Date

2011

Keywords

N95 respirator, Nano-particle, Filter, Penetration, Exposure

Abstract

With the exponential growth of the nano-technological products and their potential impact on the workers’ health and safety, the N95 filtering face-piece respirators (FFRs) are commonly recommended to protect them from the exposure to nano-particles in workplaces. This paper reports the outcomes of a series of experiments carried out to characterize the performance of NIOSH approved N95 filtering face-piece respirators against particles in nano-range: poly-dispersed and mono-dispersed sodium chloride (NaCl) particles were used in this study. In the first experimental set-up, a methodology was developed to test a N95 respirator model, sealed on a manikin head, against 15 to 200 nm poly-dispersed NaCl aerosols as function of flow rate (85, 135, 270 and 360 liters/min), loading time (up to 5 hours), and relative humidity (RH) (10, 30 and 70%). In the second phase, the experimental set-up was adapted to test N95 respirators against mono-dispersed particles (at twelve particle sizes) with a size range between 20 to 200 nm at a constant flow rate of 85 liters/min.

The results from the poly-dispersed aerosol test (PAT) method indicated that the inhalation flow rate had a strong impact on the initial particle penetration; the maximum penetration level through the N95 respirator dramatically exceeded the 5% NIOSH certification criterion at flow rates higher than 85 liters/min. The particle penetrations at the Most Penetrating Particle Size (MPPS), occurring between 30 to 50 nm, were respectively 6.6, 11.7 and 15.3% for the airflow rate of 135, 270 and 360 liters/min. The outcomes of the effect of particle loading on the filter performance showed that, the particle penetration decreased through the N95 respirator for particle sizes below 100 nm.

The mono-dispersed aerosol test (MAT) method was performed at 85 liters/min constant flow rate; the initial particle penetration at the MPPS was below 5% NIOSH certification criterion. Moreover, the initial particle penetration value, measured with (MAT) method was higher than the one measured with (PAT) method at each corresponding particle size.

Source Publication

Journal of the International Society for Respiratory Protection

Volume Number

28

Issue Number

1

First Page

26

Last Page

39

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