Errors associated with three methods of assessing respirator fit

Three fit test methods (Bitrex, saccharin, and TSI PortaCount Plus with the N95-Companion) were evaluated for their ability to identify wearers of respirators that do not provide adequate protection during a simulated workplace test. Thirty models of NIOSH-certified N95 half-facepiece respirators (15 filtering-facepiece models and 15 elastomeric models) were tested by a panel of 25 subjects using each of the three fit testing methods. Fit testing results were compared to 5th percentiles of simulated workplace protection factors. Alpha errors (the chance of failing a fit test in error) for all 30 respirators were 71% for the Bitrex method, 68% for the saccharin method, and 40% for the Companion method. Beta errors (the chance of passing a fit test in error) for all 30 respirator models combined were 8% for the Bitrex method, 8% for the saccharin method, and 9% for the Companion method. The three fit test methods had different error rates when assessed with filtering facepieces and when assessed with elastomeric respirators. For example, beta errors for the three fit test methods assessed with the 15 filtering facepiece respirators were < or = 5% but ranged from 14% to 21% when assessed with the 15 elastomeric respirators. To predict what happens in a realistic fit testing program, the data were also used to estimate the alpha and beta errors for a simulated respiratory protection program in which a wearer is given up to three trials with one respirator model to pass a fit test before moving onto another model. A subject passing with any of the three methods was considered to have passed the fit test program. The alpha and beta errors for the fit testing in this simulated respiratory protection program were 29% and 19%, respectively. Thus, it is estimated, under the conditions of the simulation, that roughly one in three respirator wearers receiving the expected reduction in exposure (with a particular model) will fail to pass (with that particular model), and that roughly one in five wearers receiving less reduction in exposure than expected will pass the fit testing program in error.     

Comparison of five methods for fit-testing N95 filtering-facepiece respirators

Five fit-testing methods (Bitrex, ambient aerosol condensation nuclei counter using the TSI PortaCount Plus, saccharin, modified ambient aerosol condensation nuclei counter using the TSI PortaCount Plus with the N95-Companion, and generated aerosol using corn oil) were evaluated for their ability to identify poorly fitting N95 filtering-facepiece respirators. Eighteen models of NIOSH-certified, N95 filtering-facepiece respirators were tested by a panel of 25 subjects using each fit-testing method. The penetration of the corn oil and the ambient aerosols through the filter media of each respirator was measured in order to adjust the corresponding generated and ambient aerosol overall fit factors, reflecting only face-seal leakage. Fit-testing results were compared to 5th percentiles of simulated workplace protection factors. Beta errors (the chance of passing a fit-test in error) ranged from 3 percent to 11 percent. Alpha errors (the chance of failing a fit-test in error) ranged from 51 percent to 84 percent. The ambient aerosol using the TSI PortaCount Plus and the generated aerosol methods identified poorly fitting respirators better than the saccharin, the Companion, and Bitrex methods. These errors rates should be considered when selecting a fit-testing method for fitting N95 filtering-facepieces. When both types of errors were combined as an assignment error, the ambient aerosol method using the TSI PortaCount Plus had the lowest percentage of wearers being assigned a poor-fitting respirator.     

Distribution of faceseal leak sites on a half-mask respirator and their association with facial dimensions

Faceseal leaks on one brand of half-mask respirator worn by 73 human subjects were identified by deposition of a fluorescent tracer aerosol during a standard quantitative fit test. The identified leaks were categorized according to their location and shape. It was found that about 89% of all observed leaks occurred at the nose or chin or were multiple leaks which included these sites. Fit factors for these types of leaks were significantly lower than for other types of leaks. About 73% of all leaks approximated the shape of a slit rather than a round orifice, and the prevalence of these leaks was affected by gender. Significant association of facial dimensions and leak sites were found. Most of these were attributed to differences in gender, and only a very small percentage were for the facial dimensions used to define the Los Alamos respirator test panel. Significant correlation of facial dimensions and fit factor were found for only three facial dimensions; none of which are used to define the test panel. Evidence of airflow streamlining within the facepiece was observed on 22% of the subjects. Results of this study indicate that respirator leakage is strongly affected by nose and chin leaks, that gender is a factor in how a respirator fits, and that consideration should be given to including nasal dimensions when defining a respirator test panel and selecting a respirator for an individual wearer.     

A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using fixed leaks

An automated version of a new method for quantitative respirator fit testing by controlled negative pressure was compared with a computerized aerosol fit test system. The controlled negative pressure technique eliminates many of the problems associated with aerosol and pressure decay fit test methods. A series of fixed leaks was used to compare the leak measurement capabilities of the controlled negative pressure system against a standard computerized aerosol fit test system. Negative pressure and aerosol fit factors determined for a series of fixed leaks through hypodermic needles were highly correlated with each other (r = 0.998) and with the cross-sectional areas of the leak needles (r greater than 0.995).     

Characteristics of face seal leakage in filtering facepieces.

Several studies have found that aerosol size, testing method, leak size, leak position, sampling probe location, and the mixing condition inside the respirator affect the results of fit factor measurements. This study focuses on the effect of leak shape and filter resistance because leaks have been reported to vary in shape from circular to slit-like. Four leaks of different shape but the same cross-sectional area were used to study their effect on aerosol penetration. Dust-mist and high-efficiency particulate air filtering facepieces provided different filter resistances. An aerodynamic particle sizer and a laser aerosol spectrometer were used to measure the particle size-dependent aerosol concentrations inside and outside the respirators. The filtering facepieces were sealed to a mannequin and artificial leaks were inserted near the right cheek. Aerosol penetration was measured for five flow rates ranging from 5 to 100 L/min. The pressure drop across the mask was monitored with an inclined manometer. At a given pressure differential, a slit-like leak and multiple circular leaks have been found to pass less aerosols than a single circular leak of equal cross-sectional area because the leak flow decreases with an increase in leak shape complexity. If there is substantial lack of face seal fit and the breathing rate is low, a HEPA respirator may provide less protection than a dust-mist respirator because the pressure drop is considerably higher for a HEPA respirator, resulting in more aerosol flow through the leak.     

Simplified pressure method for respirator fit testing

A simplified pressure method has been developed for fit testing air-purifying respirators. In this method, the air-purifying cartridges are replaced by a pressure-sensing attachment and a valve. While wearers hold their breath, a small pump extracts air from the respirator cavity until a steady-state pressure is reached in 1 to 2 sec. The flow rate through the face seal leak is a unique function of this pressure, which is determined once for all respirators, regardless of the respirator's cavity volume or deformation because of pliability. The contaminant concentration inside the respirator depends on the degree of dilution by the flow through the cartridges. The cartridge flow varies among different brands and is measured once for each brand. The ratio of cartridge to leakflow is a measure of fit. This flow ratio has been measured on human subjects and has been compared to fit factors determined on the same subjects by means of photometric and particle count tests. The aerosol tests gave higher values of fit.     

Performance of a novel real-time respirator seal integrity monitor on firefighters: Simulated workplace pilot study

Millions of workers, including firefighters, use respiratory protective device. The key aspect in assuring the intended protection level of a respirator is its fit. However, even if the respirator originally fits well, the faceseal may be breached during its use. Until now, there have been no practically viable, inexpensive means to monitor the performance of a respirator during actual use. A novel Respirator Seal Integrity Monitor (ReSIM) was developed and recently evaluated on manikins by our team. The objective of this study was to evaluate the ReSIM effectiveness on respirator-wearing firefighters exposed to aerosols while performing simulated routine operational activities. Initially, 15 subjects were recruited for the study. Following a preliminary investigation that resulted in modifications in the ReSIM prototype and testing protocol, a subset of nine firefighters was chosen for a full-scale evaluation. The testing was conducted in a 24.3-m³ exposure chamber using NaCl as the challenge aerosol. Controlled faceseal leaks were established by opening a solenoid valve for 10, 15, or 20?sec. Leaks were also established as the tested firefighter slightly repositioned the respirator on his/her face. During the testing, the ReSIM measured particles inside a full-face elastomeric respirator with a 72.7% leak detection sensitivity (probability of correct leak identification) and an 84.2% specificity (probability of correct identification of the intervals which are absent of any leak). After adjusting for false negatives and persistent false positives, sensitivity and specificity increased to 83.6% and 92.2%, respectively. The factors causing minor limitations in leak detection sensitivity and specificity can be attributed to variability among subjects, moisture’s effect on the particle sensor, and some in-mask sampling bias. In conclusion, the ReSIM can promptly detect the breach in a respirator faceseal with high sensitivity and specificity. Due to its capability to alert the wearer of possible overexposure to hazardous aerosols, the ReSIM concept has a remarkable potential to be applied in various working environments, where respirators are used.     

Determination of known exhalation valve damage using a negative pressure user seal check method on full facepiece respirators

A negative pressure user seal check (NPUSC) method was evaluated for its ability to adequately detect known exhalation valve leakage into a respirator. Three valves with different types of damage were included. Twenty-six test subjects, wearing full facepiece respirators, were asked to perform a NPUSC. Their responses as to whether they passed or failed the user seal check were compared to fit testing results from two quantitative fit test methods: ambient aerosol and controlled negative pressure. In addition, equipment developed at the University of Cincinnati was used to measure in-mask pressures that are generated during the performance of NPUSCs. This technique was employed to assess the ability of respirator wearers to properly conduct user seal checks. The data were analyzed to determine if the user seal check procedure is an effective method for detecting known exhalation valve damage. All test subjects reported passing the user seal check with the undamaged valve. With the warped valve installed, 95 percent of test subjects reported passing the user seal check. With the slit valve installed, 73 percent of test subjects reported passing. With the dirty valve installed, 65 percent reported passing. All fit factors, measured with the damaged valves, were below the Occupational Safety and Health Administration-recognized pass/fail criteria except one fit test with the respirator equipped with the slit valve. Results from the in-mask pressure measurements confirmed whether or not the subject properly conducted a user seal check, but did not detect respirator leakage. In conclusion, the performance of a NPUSC rarely helped to identify damaged exhalation valves. These results support the need for respirator inspection prior to donning with periodic fit testing and the performance of user seal checks as necessary components of an adequate respiratory protection program.     

Comparison of performance of three different types of respiratory protection devices

Respiratory protection is offered to American workers in a variety of ways to guard against potential inhalation hazards. Two of the most common ways are elastomeric N95 respirators and N95 filtering-facepiece respirators. Some in the health care industry feel that surgical masks provide an acceptable level of protection in certain situations against particular hazards. This study compared the performance of these types of respiratory protection during a simulated workplace test that measured both filter penetration and face-seal leakage. A panel of 25 test subjects with varying face sizes tested 15 models of elastomeric N95 respirators, 15 models of N95 filtering-facepiece respirators, and 6 models of surgical masks. Simulated workplace testing was conducted using a TSI PORTACOUNT Plus model 8020, and consisted of a series of seven exercises. Six simulated workplace tests were performed with redonning of the respirator/mask occurring between each test. The results of these tests produced a simulated workplace protection factor (SWPF). The geometric mean (GM) and the 5th percentile values of the SWPFs were computed by category of respiratory protection using the six overall SWPF values. The level of protection provided by each of the three respiratory protection types was compared. The GM and 5th percentile SWPF values without fit testing were used for the comparison, as surgical masks were not intended to be fit tested. The GM values were 36 for elastomeric N95 respirators, 21 for N95 filtering-facepiece respirators, and 3 for surgical masks. An analysis of variance demonstrated a statistically significant difference between all three. Elastomeric N95 respirators had the highest 5th percentile SWPF of 7. N95 filtering-facepiece respirators and surgical masks had 5th percentile SWPFs of 3 and 1, respectively. A Fisher Exact Test revealed that the 5th percentile SWPFs for all three types of respiratory protection were statistically different. In addition, both qualitative (Bitrex and saccharin) and quantitative (N95-Companion) fit testing were performed on the N95 filtering- and elastomeric-facepiece respirators. It was found that passing a fit test generally improves the protection afforded the wearer. Passing the Bitrex fit test resulted in 5th percentile SWPFs of 11.1 and 7.9 for elastomeric and filtering-facepiece respirators, respectively. After passing the saccharin tests, the elastomeric respirators provided a 5th percentile of 11.7, and the filtering-facepiece respirators provided a 5th percentile of 11.0. The 5th percentiles after passing the N95-Companion were 13.0 for the elastomeric respirators and 20.5 for the filtering-facepiece respirators. The data supports fit testing as an essential element of a complete respiratory protection program.     

Laboratory and field evaluation of a new personal sampling system for assessing the protection provided by the N95 filtering facepiece respirators against particles

OBJECTIVES: We have recently developed a new personal sampling system for the real-time measurement of the protection provided by respirators against airborne dust and micro-organisms. The objective of this study was to evaluate the performance characteristics of the new sampling system in both laboratory and field conditions. METHODS: The measurements were conducted using the N95 filtering facepiece respirators and the newly developed personal sampling system put on a manikin (laboratory study) or donned by a human subject (laboratory and field studies). Two inhalation flow rates (0 and 40 l min(-1)) in conjunction with the sampling flow rate (10 l min(-1)) were tested in the manikin-based experiments to investigate the effects of the leak location (nose, cheek and chin) and the depth of the sampling probe (0, 5, 10 and 15 mm) within the respirator. The effect of human activity on the protection factor was evaluated using a variety of head movements and breathing patterns when a human subject wore the respirator in a room-size laboratory test chamber. The field study was conducted during corn harvesting with a respirator worn by a human subject on a combine. RESULTS: There was no significant difference in the protection factors for different leak locations, or for sampling probe depths, when the inhalation rate was 0 l min(-1). For the inhalation rate of 40 l min(-1), the protection factors for nose leaks were higher than those for chin and cheek leaks. Furthermore, the protection factor was the lowest and showed the least variation when the sampling probe depth was equal to 0 mm (imbedded on the respirator surface). Human subject testing showed that the grimace maneuver decreased the protection factor and changed the original respirator fit. The protection factor during breath holding was lower than that found during inhalation and exhalation. Field results showed greater variation than laboratory results. CONCLUSIONS: The newly designed personal sampling system efficiently detected the changes in protection factors in real time. The sampling flow was least affected by the inhalation flow when the sampling probe was imbedded on the respirator surface. Leak location, breathing patterns and exercises did affect the measurement of the protection factors obtained using an N95 filtering facepiece respirator. This can be attributed to the differences in the in-mask airflow dynamics contributed by the leak, filter material, sampling probe and inhalation. In future studies, it would be beneficial if the laboratory data could be integrated with the field database.     

Impact of time and assisted donning on respirator fit

The goal of this study was to examine the impact of assistance with donning and time on quantitative fit factors (FF) and pass rates for subjects wearing an N95 filtering facepiece respirator (FFR) and a non-certified adhesive mask. Fit factors were measured using two side-by-side TSI Portacount instruments sampling second-by-second simultaneous inside- and outside-facepiece concentrations. Naïve subjects made two visits at least one week apart. At each visit subjects first donned either the respirator or adhesive mask without assistance and performed a five-exercise fast fit test. They then donned a new respirator or mask with assistance in proper donning (e.g., proper forming of the nosepiece, strap placement, etc.) and performed a second five-exercise fast fit test. The same sequence of unassisted and assisted donning was then repeated with the other facepiece. Fifteen subjects participated in the study; time between visits ranged from 7–29 days (average 12 days). On visit 1 the respirator FFs were significantly higher (GM = 88) than for the adhesive mask (GM = 14); with assistance these FFs showed significant improvements to 116 and 124, respectively. At visit 1 almost half of subjects donning the respirator without assistance achieved a passing FF of 100 or greater, while only one-fifth of subjects were able to pass the fit test wearing an adhesive mask without assistance. Pass rates improved for both groups with assistance, but more so for the adhesive mask wearers. On visit 2 the pass rates for both groups had decreased, with the adhesive mask group showing a greater decrease. With assistance, pass rates improved for both groups, but again more so for those wearing the adhesive mask. Results suggest that wearers would benefit from assistance and re-training every time they don a respirator, even if the time between donnings is as short as one or two weeks.     

Respirator leakage in the pharmaceutical industry of northwest England

Field qualitative fit tests were conducted at 10 separate companies in the Northwest of England to determine the proportion of leaking respirators in a cross-section of pharmaceutical manufacturing industries. The 3 M FT-10 Qualitative Fit Test Apparatus was used to test a total of 211 half-face particulate respirator wearers. Participants wore their own respirators and were asked to don them as they would normally. In all cases, no specific intervention had occurred prior to testing. Results indicated a failure rate of 69% (of the 211 subjects tested, 145 respirators were leaking). Successful results were not associated with the frequency of use (p = 0.71) or years of experience wearing respirators (p = 0.59). Similarly, successful results were not associated with respirator training in the current job (p = 0.38) or training in previous jobs (p = 0.49). Leakage was not consistent across the 10 companies, with two companies exhibiting a 100% failure rate while another company had 26 successful tests in 50 wearers (52% pass rate). Only 35 of the 211 participants performed a negative pressure test. Of these, 80% successfully passed the test, which was significantly greater than the 22% pass rate among those who had not performed the pressure test (p < 0.001).     

The effect of pressure drop on respirator faceseal leakage

Users of particulate air-purifying respirators are typically told to change their filters when breathing resistance becomes uncomfortable. It has been proposed that a noticeable increase in breathing resistance (pressure drop) may increase airflow through respirator faceseal leaks. This logic has been extended to suggest that respirator user exposure to contaminants may increase because of this theoretical increase in air leakage. Procedures similar to those of previous investigators were used to study this issue. Repeated faceseal leak rate measurements were made at -5.6 through -20.1 mm water pressure drops across the faceseal. Subjects were divided into two groups, representing acceptable fit or unacceptable fit, based on leak rate criteria prescribed by the Occupational Safety and Health Administration (OSHA). Subjects with acceptable fit did not experience an increase in faceseal leak rate with increased pressure drop. Leak rates for subjects with unacceptable fit were highly variable and did not show an association with pressure drop. Results of this study do not support the concept of increased faceseal leakage with increased pressure drop. The evidence does not suggest increased risk of contaminant exposure through the face seal as pressure drop increases.     

Laboratory study to assess causative factors affecting temporal changes in filtering facepiece respirator fit: part I - pilot study

The National Institute for Occupational Safety and Health is conducting a first-of-its-kind study that will assess respirator fit and facial dimension changes as a function of time and improve the scientific basis for decisions on the periodicity of fit testing. A representative sample of 220 subjects wearing filtering-facepiece respirators (FFR) will be evaluated to investigate factors that affect changes in respirator fit over time. The objective of this pilot study (n = 10) was to investigate the variation in fit test data collected in accordance with the study protocol. Inward leakage (IL) and filter penetration were measured for each donned respirator, permitting the calculation of face seal leakage (FSL) and fit factor (FF). The study included only subjects who (a) passed one of the first three fit tests (FF ≥ 100), and (b) demonstrated through a series of nine donnings that they achieved adequate fit (90th percentile FSL was ≤ 0.05). Following the respirator fit tests, 3-D scans of subjects were captured, and height, weight, and 13 traditional anthropometric facial dimensions were measured. The same data were collected 2 and 4 weeks after baseline. The mean change in FSL for the 10 subjects was 0.044% between Visits 1 and 2, and was 0.229% between Visits 1 and 3. Technicians achieved at least moderate reliability for all manual measurements except nose protrusion. Filter penetration was generally less than 0.03%. Geometric mean fit factors were not statistically different among the three visits. The large variability was observed with different respirator samples for the same model, between subjects (inter), and within each subject (intra). Although variability was observed, adequate fit was maintained for all 10 subjects. Pilot scans collected show subject faces remained the same over the 4 weeks. The consistent results during the pilot study indicate that the methods and procedures are appropriate for the 3-year main study. In addition, this baseline fit change data will be compared with future fit changes to determine if the changes are meaningful.     

Fit factors for quarter masks and facial size categories

Respirator fit testing is necessary before entering hazardous working environments to ensure that the respirator, when worn, satisfies a minimum fit and that the wearer knows when the respirator fits properly. In the many countries that do not have fit testing or total inward leakage regulations (including Korea), however, many workers wearing respirators may be potentially exposed to hazardous environments. It is necessary to suggest a useful tool to provide an alternative for fit testing in these countries. This study was conducted to evaluate fitting performance for quarter-mask respirators, and fit factors in facial size categories based on face lengths and lip lengths of the wearers. A total of 778 subjects (408 males, 370 females) were fit tested for three quarter masks: Sejin Co. SK-6 (Ulsan, Korea), Yongsung Co. YS-2010 S (Seoul, Korea), and 3 M Co. Series 7500 Medium (MN, USA) masks with a PortaCount 8020 (TSI Co., USA). A facial dimension survey of the subjects was conducted to develop facial size categories, on the basis of face length and lip length. Geometric mean fit factors (GMFFs) of Series 7500 Medium were found to be the highest of the three respirators. All of the respirators were more suitable for males than females in fitting performance. The Series 7500 Medium fitted a large number of the males tested, since the GMFFs for males were above 100 for every box of facial size categories, and high pass proportion rates were shown at an individual fit factor level of 100. The YS-2010 S provides an adequate fit for males in a limited range of facial dimensions. The Series 7500 Medium is more limited in providing adequate fit for females at specific facial dimensions than for males. For adequate fitting performance, the SK-6 is not preferentially recommended for Korean male and female workers due to low GMFFs and pass proportions. The result of this study indicates that after more accurate studies are performed, facial size categories, on the basis of facial dimensions, could be a useful tool to assist in the selection of adequately fitting respirators for workers in the countries having no fit testing requirements.     

Identification of faceseal leak sites on a half-mask respirator

A method has been developed to identify the location and shape of respirator faceseal leak sites by the deposition of a fluorescent tracer. An aerosol generation, conditioning, and exposure system to provide a test environment with stable aerosol concentration and size distribution of 4-methyl-7-diethylaminocoumarin was designed and tested. Faceseal leak sites on a respirator mounted on a mannequin and worn by human subjects were identified by deposition of the tracer aerosol and subsequent observation under long-wave ultraviolet lighting. Test parameters were identified for the optimal definition of leaks. Photographic techniques were developed to document the identified leak sites.     

Noninvasive, quantitative respirator fit testing through dynamic pressure measurement

A new method has been invented for the noninvasive and quantitative determination of fit for a respirator. The test takes a few seconds and requires less expensive instrumentation than presently used for invasive testing. In this test, the breath is held at a negative pressure for a few seconds, and the leak-induced pressure decay inside the respirator cavity is monitored. A dynamic pressure sensor is attached to a modified cartridge of an air-purifying respirator or built into the respirator body or into the air supply line of an air-supplied respirator. The method is noninvasive in that the modified cartridge can be mounted onto any air-purifying respirator. The pressure decay during testing quantifies the airflow entered through the leak site. An equation has been determined which gives the air leakage as a function of pressure decay slope, respirator volume and the pressure differential during actual wear--all of which are determined by the dynamic pressure sensor. Thus, the ratio of air inhaled through the filters or via the air supply line to the leak rate is a measure of respirator fit, independent of aerosol deposition in the lung and aerosol distribution in the respirator cavity as found for quantitative fit testing with aerosols. The new method is shown to be independent of leak and sensor locations. The concentration and distribution of aerosols entered through the leak site is dependent only on the physical dimensions of the leak site and the air velocity in it, which can be determined independently.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simulated workplace protection factors for half-facepiece respiratory protective devices

This study investigates two different methods (random effects model and 5th percentile) for determining the performance of three types of respiratory protective devices (elastomeric N95 respirators, N95 filtering-facepiece respirators, and surgical masks) during a simulated workplace test. This study recalculated the protection level of three types of respiratory protective devices using the random effects model, compared the two methods with each other and the APF of 10 for half-facepiece respirators, and determined the value of each of the fit test protocols in attaining the desired level of simulated workplace protection factor (SWPF). Twenty-five test subjects with varying face sizes tested 15 models of elastomeric N95 respirators, 15 models of N95 filtering-facepiece respirators, and 6 models of surgical masks. Simulated workplace testing was conducted using a TSI PORTACOUNT Plus model 8020 and consisted of a series of seven exercises. Six simulated workplace tests were performed with redonning of the respirator/mask occurring between each test. Each of the six tests produced an SWPF. To determine the level of protection provided by the respiratory protective devices, a 90% lower confidence limit for the simulated workplace protection factor (SWPF(LCL90%)) and the 5th percentile of simulated workplace protection factor were computed. The 5th percentile method values could be up to seven times higher than the SWPF(LCL90%) values. Without fit testing, all half-facepiece N95 respirators had a 5th percentile of 4.6 and an SWPF(LCL90%) value of 2.7. N95 filtering-facepiece respirators as a class had values of 3.3 and 2.0, respectively, whereas N95 elastomeric respirators had values of 7.3 and 4.6, respectively. Surgical masks did not provide any protection, with values of 1.2 and 1.4, respectively. Passing either the Bitrex, saccharin, or Companion fit test resulted in the respirators providing the expected level of protection with 5th percentiles greater than or equal to 10 except when passing the Bitrex test with N95 filtering-facepiece respirators, which resulted in a 5th percentile of only 7.9. No substantial difference was seen between the three fit tests. All of the SWPF(LCL90%) values after passing a fit test were less than 10. The random model method provides a more conservative estimate of the protection provided by a respirator because it takes into account both between- and within-wearer variability.     

Respiratory protection against Mycobacterium tuberculosis: quantitative fit test outcomes for five type N95 filtering-facepiece respirators

In preparing to fit test a large workforce, a respirator program manager needs to initially choose respirators that will fit the greatest proportion of employees and achieve the best fits. This article discusses our strategy in selecting respirators from an initial array of seven NIOSH-certified Type N95 filtering-facepiece devices for a respiratory protection program against Mycobacterium tuberculosis (M. tb) aerosol. The seven respirators were screened based on manufacturer-provided fit test data, comfort, and cost. From these 7 devices, 5 were chosen for quantitative fit testing on 40 subjects who were a convenience sample from a cohort of approximately 30,000 workers scheduled to undergo fit testing. Across the five brands, medium/regular-size respirators fit from 8% to 95% of the subjects; providing another size of the same brand improved the pass rates slightly. Gender was not found to significantly affect fit test pass rates for any respirator brand. Among test panel members, an Aearo Corporation respirator (TC 84A-2630) and a 3M Company respirator (TC 84A-0006) provided the highest overall pass rates of 98% and 90%, respectively. We selected these two brands for fit testing in the larger worker cohort. To date, these two respirators have provided overall pass rates of 98% (1793/1830) and 88% (50/57), respectively, which are similar to the test panel results. Among 1850 individuals who have been fit tested, 1843 (99.6%) have been successfully fitted with one or the other brand. In a separate analysis, we used the test panel pass rates to estimate the reduction in M. tb infection risk afforded by the medium/regular-size of five filtering-facepiece respirators. We posed a low-exposure versus a high-exposure scenario for health care workers and assumed that respirators could be assigned without conducting fit testing, as proposed by many hospital infection control practitioners. Among those who would pass versus fail the fit test, we assumed an average respirator penetration (primarily due to faceseal leakage) of .04 and 0.3, respectively. The respirator with the highest overall pass rate (95%) reduced M. tb infection risk by 95%, while the respirator with the lowest pass rate (8%) reduced M. tb infection risk by only 70%. To promote the marketing of respirators that will successfully fit the highest proportion of wearers, and to increase protection for workers who might use respirators without the benefit of being fit tested, we recommend that fit testing be part of the NIOSH certification process for negative-pressure air-purifying respirators with tightly fitting facepieces. At a minimum, we recommend that respirator manufacturers generate and provide pass rate data to assist in selecting candidate respirators. In any event, program managers can initially select candidate respirators by comparing quantitative fit tests for a representative sample of their employee population.     

The effects of strapped spectacles on the fit factors of three manufactured brands of full facepiece negative pressure respirators.

A study was conducted to determine the effects of strapped spectacles on the fit factors obtained during quantitative fit testing on three different brands of full facepiece negative pressure respirators. The three brands of respirators were evaluated with and without strapped spectacles worn by the test subjects. A total of 180 quantitative fit testing trials were conducted on ten male test subjects. For each test subject, three quantitative fit testing trials were performed with each brand of respirator with and without the spectacles. The average of the fit testing trials for each subject with each respirator was used for statistical analysis. The results demonstrated that the fit factor values were significantly lower during use of the spectacles (p < 0.05). The estimated percentage of test subjects who failed the American National Standards Institute pass/fail criteria for quantitative fit testing (1000) increased by 15-36% when spectacles were worn.