Respiratory Performance Offered by N95 Respirators and Surgical Masks: Human Subject Evaluation with NaCl Aerosol Representing Bacterial and Viral Particle Size Range

Lee, Shu-An; Grinshpun, Sergey A.; Reponen, Tiina

doi:10.1093/annhyg/men005

Cited by 219 publications

(229 citation statements)

References 24 publications

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“…The relationship between particle size and PF obtained in our study is corroborated by the findings in previous studies (Lee et al , 2008; Cho et al , 2010). The PF values for eight different particle size ranges between 40 to 1200 nm were measured for N95 FFRs worn by human subjects (Lee et al , 2008).…”

Section: Discussionsupporting

confidence: 93%

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Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

Rengasamy

Walbert

Newcomb

et al. 2014

The Annals of Occupational Hygiene

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A previous study used a PortaCount Plus to measure the ratio of particle concentrations outside (Cout) to inside (Cin) of filtering facepiece respirators (FFRs) worn by test subjects and calculated the total inward leakage (TIL) (Cin/Cout) to evaluate the reproducibility of the TIL test method between two different National Institute for Occupational Safety and Health laboratories (Laboratories 1 and 2) at the Pittsburgh Campus. The purpose of this study is to utilize the originally obtained PortaCount Cout/Cin ratio as a measure of protection factor (PF) and evaluate the influence of particle distribution and filter efficiency. PFs were obtained for five N95 model FFRs worn by 35 subjects for three donnings (5 models × 35 subjects × 3 donnings) for a total of 525 tests in each laboratory. The geometric mean of PFs, geometric standard deviation (GSD), and the 5th percentile values for the five N95 FFR models were calculated for the two laboratories. Filter efficiency was obtained by measuring the penetration for four models (A, B, C, and D) against Laboratory 2 aerosol using two condensation particle counters. Particle size distribution, measured using a Scanning Mobility Particle Sizer, showed a mean count median diameter (CMD) of 82 nm in Laboratory 1 and 131 nm in Laboratory 2. The smaller CMD showed relatively higher concentration of nanoparticles in Laboratory 1 than in Laboratory 2. Results showed that the PFs and 5th percentile values for two models (B and E) were larger than other three models (A, C, and D) in both laboratories. The PFs and 5th percentile values of models B and E in Laboratory 1 with a count median diameter (CMD) of 82 nm were smaller than in Laboratory 2 with a CMD of 131 nm, indicating an association between particle size distribution and PF. The three lower efficiency models (A, C, and D) showed lower PF values than the higher efficiency model B showing the influence of filter efficiency on PF value. Overall, the data show that particle size distribution and filter efficiency influence the PFs and 5th percentile values. The PFs and 5th percentile values decreased with increasing nanoparticle concentration (from CMD of 131 to 82 nm) indicating lower PFs for aerosol distribution within nanoparticle size range (<100 nm). Further studies on the relationship between particle size distribution and PF are needed to better understand the respiratory protection against nanoparticles.

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Section: Discussionsupporting

confidence: 93%

“…Similarly, PF for N95 FFRs worn by subjects was measured as a ratio of particle concentration outside to inside the respirator in a controlled test chamber, using an Electrical Low Pressure Impactor (ELPI) (Lee et al , 2008). The ELPI measures the particle concentration of different aerodynamic diameter size particles.…”

Section: Introductionmentioning

confidence: 99%

Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

Rengasamy

Walbert

Newcomb

et al. 2014

The Annals of Occupational Hygiene

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“…[ 8 , 15 ] Results showed that the number of test subjects passing the TIL test (i.e., TIL <1.0%) was significantly lower in the laboratory with a CMD of 82 nm compared to the laboratory with a CMD of 131 nm indicating the effect of particle size distribution on TIL measurement. [ 8 ] The results are consistent with the findings in other studies, [ 12 , 13 ] which showed a particle size-dependent increase in protection factor (inverse factor of TIL). Recent studies also showed TIL was particle size-dependent for different types of aerosols.…”

Section: Introductionsupporting

confidence: 91%

A comparison of total inward leakage measured using sodium chloride (NaCl) and corn oil aerosol methods for air-purifying respirators

Rengasamy

Zhuang

Niezgoda

et al. 2018

Journal of Occupational and Environmental Hygiene

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The International Organization for Standardization (ISO) standard 16900–1:2014 specifies the use of sodium chloride (NaCl) and corn oil aerosols, and sulfur hexafluoride gas for measuring total inward leakage (TIL). However, a comparison of TIL between different agents is lacking. The objective of this study was to measure and compare TIL for respirators using corn oil and NaCl aerosols. TIL was measured with 10 subjects donning two models of filtering facepiece respirators (FFRs) including FFP1, N95, P100, and elastomeric half-mask respirators (ERs) in NaCl and corn oil aerosol test chambers, using continuous sampling methods. After fit testing with a PortaCount (TSI, Inc., St. Paul, MN) using the Occupational Safety and Health Administration (OSHA) protocol, five subjects were tested in the NaCl chamber first and then in the corn oil chamber, while other subjects tested in the reverse order. TIL was measured as a ratio of mass-based aerosol concentrations in-mask to the test chamber, while the subjects performed ISO 16900–1-defined exercises. The concentration of NaCl aerosol was measured using two flame photometers, and corn oil aerosol was measured with one light scattering photometer. The same instruments were used to measure filter penetration in both chambers using a Plexiglas setup. The size distribution of aerosols was determined using a scanning mobility particle sizer and charge was measured with an electrometer. Filter efficiency was measured using an 8130 Automated Filter Tester (TSI). Results showed the geometric mean TIL for corn oil aerosol for one model each of all respirator categories, except P100, were significantly (p < 0.05) greater than for NaCl aerosol. Filter penetration in the two test chambers showed a trend similar to TIL. The count median diameter was ~ 82 nm for NaCl and ~ 200 nm for corn oil aerosols. The net positive charge for NaCl aerosol was relatively larger. Both fit factor and filter efficiency influence TIL measurement. Overall, TIL determination with aerosols of different size distributions and charges using different methodologies may produce dissimilar results.

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“…Some older studies have reported variable effectiveness against viral and bacteria-sized particles (Chen & Willeke 1992;Weber et al 1993;Chen et al 1994). Even though the materials, methods and mask designs may have changed since then, later studies on N95 masks still show variable effectiveness against viral and bacteria-sized particles (Qian et al 1998, Lee et al 2008, Johnson et al 2009). Second, the actual act of wearing masks and keeping them on in a proper position is very difficult, as multiple studies on healthcare workers (who wear masks to protect themselves from patients and patients from themselves) have shown (CDC 2009;Jacobs et al 2009, Seale et al 2009, Gershon et al 2009).…”

Section: Mitigating Transmissionmentioning

confidence: 99%

Airborne transmission of disease in hospitals

Eames

Tang

et al. 2009

J. R. Soc. Interface.

173

126

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Hospital-acquired infection (HAI) is an important public health issue with unacceptable levels of morbidity and mortality, over the last 5 years. Disease can be transmitted by air (over large distances), by direct/indirect contact or a combination of both routes. While contact transmission of disease forms the majority of HAI cases, transmission through the air is harder to control, but one where the engineering sciences can play an important role in limiting the spread. This forms the focus of this themed volume.In this paper, we describe the current hospital environment and review the contributions from microbiologists, mechanical and civil engineers, and mathematicians to this themed volume on the airborne transmission of infection in hospitals. The review also points out some of the outstanding scientific questions and possible approaches to mitigating transmission.

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Respiratory Performance Offered by N95 Respirators and Surgical Masks: Human Subject Evaluation with NaCl Aerosol Representing Bacterial and Viral Particle Size Range

Cited by 219 publications

References 24 publications

Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

A comparison of total inward leakage measured using sodium chloride (NaCl) and corn oil aerosol methods for air-purifying respirators

Airborne transmission of disease in hospitals

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