P100 Filtering Facepiece Respirators Research Articles

Performance Comparison of N95 and P100 Filtering Facepiece Respirators with Presence of Artificial Leakage

National Institute for Occupational Safety and Health-approved P100 filtering facepiece respirators (FFRs) have a higher filter efficiency compared to the N95 filters. However, the former typically produce higher flow resistance (Rf). Consequently, when faceseal leakage is present, the proportion of leakage airflow for P100 FFRs may exceed that of N95s, resulting in a higher total inward leakage (TIL) of the P100. In this manikin-based study, the performance of two pairs of N95 and P100 FFRs (N95-A versus P100-A; N95-B versus P100-B) were compared under five sealing conditions (fully sealed and partially sealed with one, two, or three leaks of 0.8-mm, and one 2-mm leak). Sodium chloride particles (CMD ~45 nm) were used as the challenge aerosol. Respirators were tested under three constant flows (15, 50, and 85 L/min) and three cyclic flows (mean inspiratory flow = 15, 50, and 85 L/min). Both filter penetration (Pfilter) and TIL were determined. The Rf under constant flows was recorded. Based on Pfilter, TIL, and Rf, the quality factor (qf) was calculated to compare the overall performance of N95 and P100 FFRs. For a fully sealed condition, the Pfilter was much lower for the P100 FFRs than for the N95 FFRs. When small leaks were inserted (0.8-mm and 2 × 0.8-mm), the TIL was higher for the P100 FFRs than for the N95 FFRs under the lowest tested flow (15 L/min), while for greater leaks (3 × 0.8-mm and 2-mm), the TIL of the P100 FFRs was always higher regardless of the flow. The Rf of P100 FFRs was measured twice as high as the N95. The qf values were also found higher for the N95 FFRs than for the P100 FFRs regardless of leak size and breathing flow. With the presence of artificial leakage, a P100 FFR with high-flow-resistance may not be as protective as a low-flow-resistance N95 FFR. This finding suggests that future efforts should be directed to reducing the breathing resistance when designing P100 FFRs.

Application of direct-reading and elemental carbon analysis methods to measure mass-based penetration of carbon nanotubes through elastomeric half-face and filtering facepiece respirators.

The aim of this study was to apply a direct-reading aerosol instrument method and an elemental carbon (EC) analysis method to measure the mass-based penetration of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) through elastomeric half-mask respirators (EHRs) and filtering facepiece respirators (FFRs). For the direct-reading aerosol instrument method, two scanning mobility particle sizer/aerodynamic particle sizer systems were used to simultaneously determine the upstream (outside respirator) and downstream (inside respirator) test aerosols. For the EC analysis method, upstream and downstream CNTs were collected on filter cassettes and then analyzed using a thermal-optical technique. CNT mass penetrations were found in both methods to be within the associated efficiency requirements for each type and class of the respirator models that were tested. Generally, the penetrations of SWCNTs and MWCNTs had a similar trend with penetration being the highest for the N95 EHRs, followed by N95 FFRs, P100 EHRs, and P100 FFRs. This trend held true for both methods; however, the CNT penetration determined by the direct-reading aerosol instrument method (0.009-1.09% for SWCNTs and 0.005-0.21% for MWCNTs) was greater relative to the penetration values found through EC analysis method (0.007-0.69% for SWCNTs and 0.004-0.13% for MWCNTs). The results of this study illustrate considerations for how the methods can be used to evaluate penetration of morphologically complex materials through FFRs and EHRs.

Measurement of mass-based carbon nanotube penetration through filtering facepiece respirator filtering media.

Recent studies suggest that a wide range of human health effects could result from exposure to carbon nanotubes (CNTs). A National Institute for Occupational Safety and Health survey of the carbonaceous nanomaterial industry found that 77% of the companies used respiratory protection, such as filtering facepiece respirators (FFRs). Despite CNT studies in some occupational settings being reported, the literature for mass-based penetration of CNTs through FFRs is lacking. The aim of this study was to conduct a quantitative study of single-walled CNT (SWCNT) and multiwalled CNT (MWCNT) penetration through FFRs. A CNT aerosol respirator testing system was used to generate charge-neutralized airborne SWCNTs and MWCNTs for this study. The size distribution was 20-10000 nm, with 99% of the particles between 25 and 2840 nm. Mass median diameters were 598 and 634 nm with geometric standard deviations of 1.34 and 1.48 for SWCNTs and MWCNTs, respectively. Upstream and downstream CNTs were collected simultaneously using closed-face 3.7-cm-diameter filter cassettes. These samples were subsequently analyzed for organic carbon and elemental carbon (EC), with EC as a measure of mass-based CNTs. The mass-based penetration of SWCNTs and MWCNTs through six FFR models at constant flow rates of 30 l min(-1) (LPM) was determined. Generally, the penetrations of SWCNTs and MWCNTs at 30 LPM had a similar trend and were highest for the N95 FFRs, followed by N99 and P100 FFRs. The mass-based penetration of MWCNTs through six FFR models at two constant flow rates of 30 and 85 LPM was also determined. The penetration of MWCNTs at 85 LPM was greater compared with the values of MWCNTs at 30 LPM.

Viable Viral Efficiency of N95 and P100 Respirator Filters at Constant and Cyclic Flow

The growing threat of an influenza pandemic presents a unique challenge to healthcare workers, emergency responders, and the civilian population. The Occupational Safety and Health Administration (OSHA) recommends National Institute for Occupational Safety and Health (NIOSH)-approved respirators to provide protection against infectious airborne viruses in various workplace settings. The filtration efficiency of selected NIOSH-approved particulate N95 and P100 filtering facepiece respirators (FFRs) and filter cartridges was investigated against the viable MS2 virus, a non-pathogenic bacteriophage, aerosolized from a liquid suspension. Tests were performed under two cyclic flow conditions (minute volumes of 85 and 135 L/min) and two constant flow rates (85 and 270 L/min). The mean penetrations of viable MS2 through the N95 and P100 FFRs/cartridges were typically less than 2 and 0.03%, respectively, under all flow conditions. All N95 and P100 FFR and cartridge models assessed in this study, therefore, met or exceeded their respective efficiency ratings of 95 and 99.97% against the viable MS2 test aerosol, even under the very high flow conditions. These NIOSH-approved FFRs and particulate respirators equipped with these cartridges can be anticipated to achieve expected levels of protection (consistent with their assigned protection factor) against airborne viral agents, provided that they are properly selected, fitted, worn, and maintained.

Filter Performance Degradation of Electrostatic N95 and P100 Filtering Facepiece Respirators by Dioctyl Phthalate Aerosol Loading

Polydisperse dioctyl phthalate (DOP) aerosols are employed for testing filter penetration with loading of R- and P-series particulate filters for National Institute for Occupational Safety and Health (NIOSH) certification. Penetration for filters must not exceed NIOSH allowed maximum levels during the entire loading of 200 mg DOP indicating no filter degradation. Degradation of respirators loaded with DOP by other aerosols as well as respirators exposed to both oil and non-oil aerosols found in some workplaces is not well studied. To better understand the degradation of respirators with electrostatic filter media, two models of N95 and P100 filtering facepiece respirators (FFRs) were loaded with polydisperse DOP aerosols up to 200 mg as employed for NIOSH certification testing with simultaneous measurement of filter penetration. In parallel experiments, both N95 and P100 FFRs were loaded with 10 to 200 mg DOP and challenged with polydisperse NaCl aerosol employed for NIOSH certification testing as well as monodisperse NaCl aerosol, and filter penetration was measured. Results showed that filter penetration for both N95 models increased with increasing amounts of DOP loading and exceeded NIOSH allowed maximum penetration (5%) by both DOP and NaCl aerosols indicating filter degradation. Monodisperse NaCl aerosols (20–400 nm) gradually increased the penetration and shifted the most penetrating particle size from ~40 nm to larger sizes. In the case of P100 FFRs, DOP aerosol penetration was below 0.03% for up to 200 mg DOP loading as required for NIOSH certification. Interestingly, one of the two P100 FFR models loaded with 10–50 mg DOP showed >0.03% penetration with polydisperse, as well as monodisperse, NaCl aerosol testing. Overall, the results obtained in the study indicate that some P100 models loaded with DOP at lower amounts may show higher penetration with other aerosols such as NaCl. Further studies are needed to better understand the filter degradation of DOP loaded respirators.

Development of a new test system to determine penetration of multi-walled carbon nanotubes through filtering facepiece respirators

Carbon nanotubes (CNTs) are currently used in numerous industrial and biomedical applications. Recent studies suggest that workers may be at risk of adverse health effects if they are exposed to CNTs. A National Institute for Occupational Safety and Health (NIOSH) survey of the carbonaceous nanomaterial industry found that 77% of the companies used respiratory protection. Elastomeric half-mask respirators and filtering facepiece respirators (FFRs) are commonly used. Although numerous respirator filtration studies have been done with surrogate engineered nanoparticles, such as sodium chloride, penetration data from engineered nanoparticles such as CNTs are lacking. The aims of this study were to develop a new CNT aerosol respirator testing system and to determine multi-walled CNT (MWCNT) penetration through FFRs.A custom-designed CNT aerosol respirator testing system (CNT-ARTS) was developed which was capable of producing a sufficient amount of airborne MWCNTs for testing of high efficiency FFRs. The size distribution of airborne MWCNTs was 20–10,000nm, with 99% of the particles between 25 and 2840nm. The count median diameter (CMD) was 209nm with a geometric standard deviation (GSD) of 1.98. This particle size range is similar to those found in some work environments (particles ≤6000nm). The penetration of MWCNTs through six tested FFR models at two constant flow rates of 30 and 85 LPM was determined. Penetration at 85 LPM (0.58–2.04% for N95, 0.15–0.32% for N99, and 0.007–0.009% for P100 FFRs) was greater compared with the values at 30 LPM (0.28–1.79% for N95, 0.10–0.24% for N99, and 0.005–0.006% for P100 FFRs). The most penetrating particle size through all six tested FFR models was found to be in the range of 25–130nm and 35–200nm for the 30-LPM and 85-LPM flow rates, respectively.

Performance of Conventional and Antimicrobial-Treated Filtering Facepiece Respirators Challenged with Biological Aerosols

This study evaluated the filtration performance of four commercially available models of National Institute of Occupational Safety and Health (NIOSH)-certified filtering facepiece respirators (FFR) against both biological and inert aerosols at a flow rate of 85 L/min. Conventional N95 and P100 FFRs and two antimicrobial (AM)-treated FFRs (an N95 and a P95, both with iodine-based AM treatments) were tested for both physical penetration (PENP) and viable penetration (PENV) with three different bioaerosols, including MS2 bacteriophage virus, and the spores and vegetative cells of Bacillus atrophaeus bacteria, in addition to inert sodium chloride (NaCl) aerosol. For each FFR model, the PENP measured with NaCl was predictive of its MS2 PENP, and it was observed that spores and bacteria aerosols were also filtered similarly to the inert aerosol. For both conventional FFRs, up to a 1-log reduction in PENV in comparison with PENP was observed and attributed to the experimental variability of the test system. For both models of AM-FFRs, no statistically significant differences between PENV and PENP for any of the three different bioaerosol challenges were observed. Thus, no bioaerosol filtration enhancement over the conventional FFRs was detected for either iodine-based AM-FFR. In the absence of any standardized test methods, we recommend that future studies evaluating the filtration performance of AM-treated FFRs incorporate the experimental best practices described herein. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a pdf file containing I. Review of Research on Antimicrobial-Treated Respirators, and II. Microorganism Propagation, Plating, and Enumeration Protocols.]

Evaluation of Five Decontamination Methods for Filtering Facepiece Respirators

Concerns have been raised regarding the availability of National Institute for Occupational Safety and Health (NIOSH)-certified N95 filtering facepiece respirators (FFRs) during an influenza pandemic. One possible strategy to mitigate a respirator shortage is to reuse FFRs following a biological decontamination process to render infectious material on the FFR inactive. However, little data exist on the effects of decontamination methods on respirator integrity and performance. This study evaluated five decontamination methods [ultraviolet germicidal irradiation (UVGI), ethylene oxide, vaporized hydrogen peroxide (VHP), microwave oven irradiation, and bleach] using nine models of NIOSH-certified respirators (three models each of N95 FFRs, surgical N95 respirators, and P100 FFRs) to determine which methods should be considered for future research studies. Following treatment by each decontamination method, the FFRs were evaluated for changes in physical appearance, odor, and laboratory performance (filter aerosol penetration and filter airflow resistance). Additional experiments (dry heat laboratory oven exposures, off-gassing, and FFR hydrophobicity) were subsequently conducted to better understand material properties and possible health risks to the respirator user following decontamination. However, this study did not assess the efficiency of the decontamination methods to inactivate viable microorganisms. Microwave oven irradiation melted samples from two FFR models. The remainder of the FFR samples that had been decontaminated had expected levels of filter aerosol penetration and filter airflow resistance. The scent of bleach remained noticeable following overnight drying and low levels of chlorine gas were found to off-gas from bleach-decontaminated FFRs when rehydrated with deionized water. UVGI, ethylene oxide (EtO), and VHP were found to be the most promising decontamination methods; however, concerns remain about the throughput capabilities for EtO and VHP. Further research is needed before any specific decontamination methods can be recommended.

Comparison of Nanoparticle Filtration Performance of NIOSH-approved and CE-Marked Particulate Filtering Facepiece Respirators

The National Institute for Occupational Safety and Health (NIOSH) and European Norms (ENs) employ different test protocols for evaluation of air-purifying particulate respirators commonly referred to as filtering facepiece respirators (FFR). The relative performance of the NIOSH-approved and EN-certified 'Conformité Européen' (CE)-marked FFR is not well studied. NIOSH requires a minimum of 95 and 99.97% efficiencies for N95 and P100 FFR, respectively; meanwhile, the EN requires 94 and 99% efficiencies for FFRs, class P2 (FFP2) and class P3 (FFP3), respectively. To better understand the filtration performance of NIOSH- and CE-marked FFRs, initial penetration levels of N95, P100, FFP2 and FFP3 respirators were measured using a series of polydisperse and monodisperse aerosol test methods and compared. Initial penetration levels of polydisperse NaCl aerosols [mass median diameter (MMD) of 238 nm] were measured using a method similar to the NIOSH respirator certification test method. Monodisperse aerosol penetrations were measured using silver particles for 4-30 nm and NaCl particles for 20-400 nm ranges. Two models for each FFR type were selected and five samples from each model were tested against charge neutralized aerosol particles at 85 l min(-1) flow rate. Penetrations from the 238 nm MMD polydisperse aerosol test were <1% for N95 and FFP2 models and <0.03% for P100 and FFP3 models. Monodisperse aerosol penetration levels showed that the most penetrating particle size (MPPS) was in the 30-60 nm range for all models of FFRs tested in the study. Percentage penetrations at the MPPS were <4.28, <2.22, <0.009 and <0.164 for the N95, FFP2, P100 and FFP3 respirator models, respectively. The MPPS obtained for all four FFR types suggested particle capturing by electrostatic mechanism. Liquid isopropanol treatment of FFRs shifted the MPPS to 200-300 nm and dramatically increased polydisperse as well as monodisperse aerosol penetrations of all four FFR types indicating that all the four FFR types share filtration characteristics of electret filters. Electrostatic charge removal from all four FFR types also increased penetration levels of 400-1000 nm range particles. Particle penetration data obtained in this study showed that the eight models of NIOSH-approved N95 and P100 and CE-marked FFP2 and FFP3 respirators used in this study provided expected levels of laboratory filtration performance against nanoparticles.

N95 and P100 Respirator Filter Efficiency Under High Constant and Cyclic Flow

This study investigated the effect of high flow conditions on aerosol penetration and the relationship between penetration at constant and cyclic flow conditions. National Institute for Occupational Safety and Health (NIOSH)-approved N95 and P100 filtering facepiece respirators and cartridges were challenged with inert solid and oil aerosols. A combination of monodisperse aerosol and size-specific aerosol measurement equipment allowed count-based penetration measurement of particles with nominal diameters ranging from 0.02 to 2.9 μm. Three constant flow conditions (85, 270, and 360 L/min) were selected to match the minute, inhalation mean, and inhalation peak flows of the four cyclic flow conditions (40, 85, 115, and 135 L/min) tested. As expected, penetration was found to increase under increased constant and cyclic flow conditions. The most penetrating particle size (MPPS) generally ranged from 0.05 to 0.2 μm for P100 filters and was approximately 0.05 μm for N95 filters. Although penetration increased at the high flow conditions, the MPPS was relatively unaffected by flow. Of the constant flows tested, the flows equivalent to cyclic inhalation mean and peak flows best approximated the penetration measurements of the corresponding cyclic flows.

Filtration Performance of NIOSH-Approved N95 and P100 Filtering Facepiece Respirators Against 4 to 30 Nanometer-Size Nanoparticles

This study investigated the filtration performance of NIOSH-approved N95 and P100 filtering facepiece respirators (FFR) against six different monodisperse silver aerosol particles in the range of 4–30 nm diameter. A particle test system was developed and standardized for measuring the penetration of monodisperse silver particles. For respirator testing, five models of N95 and two models of P100 filtering facepiece respirators were challenged with monodisperse silver aerosol particles of 4, 8, 12, 16, 20, and 30 nm at 85 L/min flow rate and percentage penetrations were measured. Consistent with single-fiber filtration theory, N95 and P100 respirators challenged with silver monodisperse particles showed a decrease in percentage penetration with a decrease in particle diameter down to 4 nm. Penetrations less than 1 particle/30 min for 4–8 nm particles for one P100 respirator model, and 4–12 nm particles for the other P100 model, were observed. Experiments were also carried out with larger than 20 nm monodisperse NaCl particles using a TSI 3160 Fractional Efficiency Tester. NaCl aerosol penetration levels of 20 nm and 30 nm (overlapping sizes) particles were compared with silver aerosols of the same sizes by a three-way ANOVA analysis. A significant (p < 0.001) difference between NaCl and silver aerosol penetration levels was obtained after adjusting for particle sizes and manufacturers. A significant (p = 0.001) interaction with manufacturers indicated the difference in NaCl, and silver aerosol penetrations were not the same across manufacturers. The two aerosols had the same effect across 20 nm and 30 nm sizes as shown by the absence of any significant (p = 0.163) interaction with particle sizes. In the case of P100 FFRs, a significant (p < 0.001) difference between NaCl and silver aerosol (20 nm and 30 nm) penetrations was observed for both respirator models tested. The filtration data for 4–30 nm monodisperse particles supports previous studies that indicate NIOSH-approved air-purifying respirators provide expected levels of filtration protection against nanoparticles.