Correlations between workplace protection factors and fit factors for filtering facepieces in the welding workplace

Workplace protection factor (WPF) means a measure of the actual protection of respirator provided in the workplace when correctly worn. While fit factor (FF) represents a quantitative measure of the fit of a particular respirator to an individual and it is determined in the laboratory. To evaluate the relationship between WPF and FF is very important since FF may or may not be taken advantage of estimating WPF. Outside and inside Fe concentrations for three brand N95 filtering facepieces were collected on 14 workers/three respirator combinations in the welding workplace. The WPF measurements on the samples of the three respirator brands worn by 14 workers were observed to range from 2.2 to 132.9 with a geometric mean of 15.9 and a geometric standard deviation of 2.63. Respirator performances as measured by the WPF differed significantly among different respirator brands (p<0.05). In this study, correlations were found between the WPF measurements and the FF data for all samples of the three respirators (R2=0.38). The percentage of Fe particles having a smaller fraction than 1.1 microm diameter was observed as 71.6% of the total.     

Statistical issues with respect to workplace protection factors for respirators

A workplace protection factor (WPF) for a respirator wearer is the measured concentration of a contaminant outside the respirator divided by the simultaneous concentration of that contaminant inside the respirator. The Occupational Safety and Health Administration (OSHA) proposed an assigned protection factor (APF) of 10 to negative-pressure, half-facepiece, air-purifying respirators (HFAPR), based on the criterion that the 5th percentile of WPF for HFAPR be larger than the APF. This class of half-facepiece respirators includes both filtering facepiece and elastomeric half-mask respirators. Nicas and Neuhaus developed a statistical model for log-normally distributed WPF that separated between-wearer and within-wearer variation. Using results from applying this model to seven studies of HFAPR, they proposed an APF of 5 for this class of respirator, based on the criterion that the 5th percentile of the 5th percentile of individual worker WPF distributions be larger than the APF. In this article, two reasons are suggested for these differing proposals: (1) the Nicas and Neuhaus criterion is inherently more conservative than that of OSHA, and (2) substantially different databases were used to evaluate the two criteria. The Nicas and Neuhaus model is expanded to allow for differences in WPF distributions for different types of HFAPR and different contaminants and for separately estimating within-wearer variation and variation due to measurement error. Appropriate statistical methods are illustrated for implementing these models when some of inside-the-respirator measurements are nondetects. Results from applying this expanded model to two new WPF studies suggest that an APF of 10 would be sufficiently protective in these studies using the OSHA criterion but more marginally so using the Nicas and Neuhaus criterion.     

Correlation between quantitative fit factors and workplace protection factors measured in actual workplace environments at a steel foundry

Past studies have found little or no correlation between workplace protection factors (WPFs) and quantitative fit factors (FFs). This study investigated the effect of good- and poor-fitting half-facepiece, air-purifying respirators on protection in actual workplace environments at a steel foundry and the correlation between WPFs and FFs. Fifteen burners and welders, who wore respirators voluntarily, and chippers participated in this study. Each subject was fit-tested with two respirator models each with three sizes, for a total of six fit-tests. Models and sizes were assigned this way to provide a wide range of FFs among study participants. Each worker donned the respirator twice per day (at the beginning of the shift and following the lunch break) for 2 days. Quantitative FFs were first obtained for each donning using the PortaCount Plus trade mark in a separate room. Without redonning the respirators, workers performed normal work for 1 to 2 hours, and WPFs were measured by collecting ambient and in-facepiece samples simultaneously. A second fit-test was conducted without disturbing the respirator. FFs were obtained by averaging the results from the first and second fit-tests. The resulting FFs had a geometric mean (GM) of 400 (range=10-6010) and a geometric standard deviation (GSD) of 6.1. Of the 55 valid donnings, 43 were good fitting (FFs> or =100) and 12 were poor fitting (FFs<100). The WPFs had a GM of 920 (range=13-230,000) and a GSD of 17.8. The WPFs were found to be significantly correlated with the FFs (R(2)=.55 and p-value=.0001). Therefore, FF was shown to be a meaningful indicator of respirator performance in actual workplace environments.     

Workplace protection factors for an N95 filtering facepiece respirator

This study evaluated the workplace performance of an N95 filtering facepiece, air-purifying respirator in a steel foundry. Air samples were collected inside and outside respirators worn by workers who were properly trained and qualitatively fit tested. For most workers, three or four pairs of air samples were collected on each of 2 days. The 49 valid sample sets were analyzed for iron, silicon, and zirconium. Only iron was present in sufficient concentrations to perform workplace protection factor (WPF) calculations. Individual WPF measurements ranged from 5 to 753. The geometric mean of the distribution was 119 with a lower 5th percentile value of 19. Time-weighted average WPFs (WPF(TWA)) were also calculated for each day for each worker as an estimate of the protection an individual might receive with daily respirator use. The WPF(TWA) values ranged from 15 for the worker with the single WPF value of 5, to a high of 684. The distribution of WPF(TWA) had a geometric mean of 120 and a lower 5th percentile of 22. Both data treatments indicate this respirator's performance was consistent with the assigned protection factor of 10 typically used for half facepiece respirators. The respirator provided adequate protection as used in this study. All contaminant concentrations inside the respirator were well below the relevant occupational exposure limits. Data collected also illustrate the dynamic nature of faceseal leakage in the workplace.     

Isocyanate exposures in autobody shop work: the SPRAY study

Isocyanates, known to cause respiratory sensitization and asthma, are widely used in automotive refinishing where exposures to aliphatic polyisocyanates occur by both inhalation and skin contact. The work reported here, the characterization of isocyanate exposure in the autobody industry, was part of an epidemiologic study of workers in 37 autobody shops in Connecticut. This article describes workplaces, tasks, and controls, and outlines the frequency, duration, and intensity of isocyanate exposures. Personal air samples taken outside of respirators had median concentrations of 66.5 microg NCO/m3 for primer, 134.4 microg (NCO)/m3 for sealer, and 358.5 microg NCO/m3 for clearcoat. Forty-eight percent of primer, 66% of sealer, and 92% of clearcoat samples exceeded the United Kingdom Health and Safety Executive guideline for isocyanate, though none exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit for monomer. Nonisocyanate-containing primers and sealers are used in more than half the shops, but nonisocyanate clearcoats are rare. Eighty-two percent of personal samples taken within a spray booth exceeded the U.K. guideline: 81% of those in downdraft spray booths, 74% in semidowndraft booths, and 92% in crossdraft booths. Only 8% of shops reported that spraying is done exclusively in spray booths. All painters wore some type of respirator. In 30% of shops, painters used supplied air respirators; the rest relied on half face organic vapor cartridge respirators with N95 overspray pads. All shops provided some type of gloves, usually latex, not recommended for isocyanate protection. Despite improvements in autobody shop materials, practices, and controls, there are still opportunities for substantial exposures to isocyanates.     

Performance of a full facepiece, air-purifying respirator against lead aerosols in a workplace environment

This study evaluated workplace performance of a full facepiece, negative pressure, air-purifying respirator with P100 filters in a lead refining plant. Air samples for lead were collected inside and outside the respirators worn by workers who were properly trained and quantitatively fit tested. Trained observers assisted in the study to ensure sample validity. Three to four pairs of air samples per day were collected from each worker for a total of 52 valid sample sets. Lead was found on all the outside samples, and concentrations were below the detection limit for all but one of the inside samples. The single measurable inside sample yielded a workplace protection factor (WPF) of 297. WPFs for the rest of the samples were estimated using the assumption that lead was present at the detection limit for the in-facepiece samples. Calculated WPFs were rounded down to the nearest 100 then subjected to a rank and percentile function. The 5th percentile WPF was approximately 900 using this approach. These WPFs exceed the assigned protection factor (APF) of 50 for this respirator class recommended by the National Institute for Occupational Safety and Health and listed by the Occupational Safety and Health Administration. These results support the APF of 50 for this respirator and indicate the respirator provided adequate protection as used in this study.     

Evaluation of air-purifying respirators for protection against toluene diisocyanate vapors

Two brands of air-purifying organic vapor cartridges (Willson and Survivair) and a disposable respirator (3M) were evaluated for protection against toluene diisocyanate (TDI) vapors. The respirators/cartridges were tested by generating dynamic atmospheres of TDI at concentrations of 0.2 and 1.5 ppm or greater, which are substantially above the currently accepted exposure limits. The TDI atmospheres were generated by controlled and continuous evaporation and dilution techniques. The relative humidity of the final TDI atmosphere was maintained at 50%. For the testing of Survivair and Willson respirators, one cartridge was mounted on a stainless steel plate and placed inside an exposure chamber through which air was drawn unidirectionally at 32 L/min. Periodically, the air before and after the cartridge was monitored for TDI. In the case of the disposable, valveless 3M respirator, a breathing pump was used to simulate the breathing through the respirator. The TDI atmosphere was respired through the respirator at 28.8 L/min (24 cycles/min at 1.2 L/cycle). As before, the concentration of TDI was measured periodically before and after the respirator. There was no significant breakthrough (less than 0.5%) of TDI in any of the respirators tested for 40 hr at 0.2 ppm and for 20 hr at 1.5 ppm or higher concentration of TDI. The detection limits of the post-respirator TDI measurements ranged from 0.4 to 0.02% of the pre-respirator concentration. It is important to note that, at the present time, because the odor threshold for TDI is higher than the ceiling exposure limit (poor warning property), NIOSH and most of the respirator manufacturers do not recommend the use of air-purifying respirators in isocyanate containing environments.     

Effectiveness of a positive pressure respirator for controlling lead exposure in acid storage battery manufacturing

Effective protection factors for lead-acid storage battery manufacturing workers using powered air-purifying respirators and their corresponding blood lead histories are reported and compared with results for half-mask, negative pressure respirators. Airborne lead protection factors for the powered, air-purifying respirator ranged from 2 to 74, while lead levels in the blood remained stable or decreased for 8 of the 13 workers monitored when compared to negative pressure respirator use levels.     

Airborne isocyanate exposures in the collision repair industry and a comparison to occupational exposure limits

Isocyanate exposure was evaluated in 33 spray painters from 25 Washington State autobody shops. Personal breathing zone samples (n = 228) were analyzed for isophorone diisocyanate (IPDI) monomer, 1,6-hexamethylene diisocyanate (HDI) monomer, IPDI polyisocyanate, and three polyisocyanate forms of HDI. The objective was to describe exposures to isocyanates while spray painting, compare them with short-term exposure limits (STELs), and describe the isocyanate composition in the samples. The composition of polyisocyanates (IPDI and HDI) in the samples varied greatly, with maximum amounts ranging from up to 58% for HDI biuret to 96% for HDI isocyanurate. There was a significant inverse relationship between the percentage composition of HDI isocyanurate to IPDI and to HDI uretdione. Two 15-min STELs were compared: (1) Oregon's Occupational Safety and Health Administration (OR-OSHA) STEL of 1000 μg/m(3) for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 μg NCO/m(3) for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UK-HSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OR-OSHA and the UK-HSE STELs as benchmarks, 21% and 67% of painters, respectively, had at least one exposure that exceeded the respirator's OSHA-assigned protection factor. A critical review of the STELs revealed the following limitations: (1) the OR-OSHA STEL does not include all polyisocyanates, and (2) the UK-HSE STEL is derived from monomeric isocyanates, whereas the species present in typical spray coatings are polyisocyanates. In conclusion, the variable mixtures of isocyanates used by autobody painters suggest that an occupational exposure limit is required that includes all polyisocyanates. Despite the limitations of the STELs, we determined that a respirator with an assigned protection factor of 25 or greater is required to protect against isocyanate exposures during spray painting. Consequently, half-face air-purifying respirators, which are most commonly used and have an assigned protection factor of 10, do not afford adequate respiratory protection.     

A survey of private sector respirator use in the United States: an overview of findings

Limitations of previous surveys of respirator use led the National Institute for Occupational Safety and Health (NIOSH) and the Bureau of Labor Statistics to undertake a survey of respirator use and practices among U.S. private sector employers. The survey was mailed to 40,002 private sector establishments in August 2001; the responses were used to develop national estimates. Respirator use was required in 4.5% of establishments and for 3.1% of employees. Of the establishments requiring respirator use, 95% used air-purifying respirators and 17% used air-supplied respirators. Manufacturing; mining (including oil and gas extraction); construction; and agriculture, forestry, and fishing had the highest rates of establishment respirator use. Respirators were used most frequently to protect against dust/mist, paint vapors, and solvents. Large percentages of establishments requiring respirator use had indicators of potentially inadequate respirator programs. Of establishments requiring respirator use, 91% had at least one indicator of a potentially inadequate respiratory protection program, while 54% had at least five indicators. The survey findings suggest that large numbers of employers may not follow NIOSH recommendations and Occupational Safety and Health Administration (OSHA) and Mine Safety and Health Administration (MSHA) requirements for the selection and use of respirators, potentially putting workers at risk. The findings will aid efforts to increase the appropriate use of respirators in the workplace.     

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.     

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.     

Evaluation of the efficiency of respiratory protective equipment based on the biological monitoring of styrene in fibreglass reinforced plastics industries

The purpose of the present study was to determine the efficiency of respiratory protective equipment in a fibreglass reinforced plastic factory by comparing results of environmental and biological monitoring of exposure to styrene. Five factories including 39 workers were investigated. Three types of respiratory protective equipment were tested: one was a half-mask air-purifying respirator equipped with a cartridge for organic solvents, another was a disposable gauze respirator impregnated with charcoal filter, and the third was a dust-proof respirator. The frequency of cartridge exchange of a half-mask respirator was twice a day only at one factory, and that was less than once a month at other factories. The site concentrations exceeded 20 ppm at 10 of the 82 sampling points (12.2%), and 22 of the 39 workers' (56.4%) personal exposure exceeded 20 ppm which is the current occupational exposure limit recommended by the Japan Society for Occupational Health. The efficiency of disposable gauze respirators and dust-proof respirators was low or rather zero. The average efficiency of half-mask respirators in which cartridges were exchanged twice a day and once a month was 83.6% and 46.6%, respectively. There was a significant disparity in the efficiency of the respirator depending on the frequency of cartridge exchange (p<0.05). Overall this study showed that even though a half-mask respirator is used and its cartridge is exchanged every half a day, workers exposed to a styrene concentration at or over 122 ppm are expected to inhale more than 20 ppm of styrene.     

The effect of subject characteristics and respirator features on respirator fit

A recent study was conducted to compare five fit test methods for screening out poor-fitting N95 filtering-facepiece respirators. Eighteen models of NIOSH-certified, N95 filtering-facepiece respirators were used to assess the fit test methods by using a simulated workplace protection factor (SWPF) test. The purpose of this companion study was to investigate the effect of subject characteristics (gender and face dimensions) and respirator features on respirator fit. The respirator features studied were design style (folding and cup style) and number of sizes available (one size fits all, two sizes, and three sizes). Thirty-three subjects participated in this study. Each was measured for 12 face dimensions using traditional calipers and tape. From this group, 25 subjects with face size categories 1 to 10 tested each respirator. The SWPF test protocol entailed using the PortaCount Plus to determine a SWPF based on total penetration (face-seal leakage plus filter penetration) while the subject performed six simulated workplace movements. Six tests were conducted for each subject/respirator model combination with redonning between tests. The respirator design style (folding style and cup style) did not have a significant effect on respirator fit in this study. The number of respirator sizes available for a model had significant impact on respirator fit on the panel for cup-style respirators with one and two sizes available. There was no significant difference in the geometric mean fit factor between male and female subjects for 16 of the 18 respirator models. Subsets of one to six face dimensions were found to be significantly correlated with SWPFs (p < 0.05) in 16 of the 33 respirator model/respirator size combinations. Bigonial breadth, face width, face length, and nose protrusion appeared the most in subsets (five or six) of face dimensions and their multiple linear regression coefficients were significantly different from zero (p < 0.05). Lip length was found in only one subset. The use of face length and lip length as the criteria to define the current half-facepiece respirator fit test panel may need to be reconsidered when revising the panel. Based on the findings from this and previous studies, face length and face width are recommended measurements that should be used for defining the panel for half-facepiece respirators.     

Method development study for APR cartridge evaluation in fire overhaul exposures

In the US, firefighters do not typically wear respiratory protection during overhaul activities, although fitting multi-gas or chemical, biological, radiological and nuclear cartridges to supplied air respirator facepieces has been proposed to reduce exposures. This work developed a method to evaluate the effectiveness of respirator cartridges in smoke that represents overhaul exposures to residential fires. Chamber and penetration concentrations were measured for 91 contaminants, including aldehydes, polynuclear aromatic hydrocarbons, hydrocarbons and methyl isothiocyanate, along with total and respirable particulates. These laboratory tests generated concentrations in the range of field-reported exposures from overhaul activities. With limited tests, no styrene, benzene, acrolein or particulates were detected in air filtered by the respirator cartridge, yet other compounds were detected penetrating the respirator. Because of the complexity of smoke, an exposure index was determined for challenge and filtered air to determine the relative risk of the aggregate exposure to respiratory irritants. The primary contributors to the irritant exposure index in air filtered by the respirator were formaldehyde and acetaldehyde, with total hydrocarbons contributing only 1% to the irritant index. Respirator cartridges were adequate to minimize firefighter exposures to aggregate respiratory irritants if the American Conference of Governmental Industrial Hygienists ceiling limit for formaldehyde is used (0.3 ppm) but not if National Institute for Occupational Safety and Health Recommended Exposure Limit (NIOSH REL) (0.1 ppm) is used, where three of five concentrations in filtered air exceeded the NIOSH REL. Respirator certification allows 1 ppm of formaldehyde to pass through it when challenged at 100 ppm, which may not adequately protect workers to current short-term exposure/ceiling limits. The method developed here recommends specific contaminants to measure in future work (formaldehyde, acrolein, acetaldehyde, naphthalene, benzene, total hydrocarbons as toluene and particulate mass) along with inclusion of additional irritant gases and hydrogen cyanide to fully evaluate whether air-purifying respirators reduce exposures to the aggregate gases/vapors present in overhaul activities.     

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.     

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.     

Correlation between respirator fit and respirator fit test panel cells by respirator size

The National Institute for Occupational Safety and Health (NIOSH), recognizing the difficulties inherent in using old military data to define modern industrial respirator fit test panels, recently completed a study to develop an anthropometric database of the measurements of heads and faces of civilian respirator users. Based on the data collected, NIOSH researchers developed two new panels for fit testing half-facepiece and full-facepiece respirators. One of the new panels (NIOSH bivariate panel) uses face length and face width. The other panel is based on principal component analysis (PCA) to identify the linear combination of facial dimensions that best explains facial variations. The objective of this study was to investigate the correlation between respirator fit and the new NIOSH respirator fit test panel cells for various respirator sizes. This study was carried out on 30 subjects that were selected in part using the new NIOSH bivariate panel. Fit tests were conducted on the test subjects using a PORTACOUNT device and three exercises. Each subject was tested with three replications of four models of P-100 half-facepiece respirators in three sizes. This study found that respirator size significantly influenced fit within a given panel cell. Face size categories also matched the respirator sizing reasonably well, in that the small, medium, and large face size categories achieved the highest geometric mean fit factors in the small, medium, and large respirator sizes, respectively. The same pattern holds for fit test passing rate. Therefore, a correlation was found between respirator fit and the new NIOSH bivariate fit test panel cells for various respirator sizes. Face sizes classified by the PCA panel also followed a similar pattern with respirator fit although not quite as consistently. For the LANL panel, however, both small and medium faces achieved best fit in small size respirators, and large faces achieved best fit in medium respirators. These findings support the selection of the facial dimensions for developing the new NIOSH bivariate respirator fit test panel.     

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.     

Assessment of the effectiveness of respirator usage in coke oven workers

This program protection factor study was conducted to evaluate the effectiveness of filter cartridge respirators while coke oven workers performed their normal work. Benzene soluble fraction (BSF) of total particulate concentrations was measured inside and outside the respirators of nine coke oven workers who worked on the top of the battery of one older coke oven plant and who reported regular use of respirators. The measurements were taken for 3 consecutive days. Excluding two undetectable measurements inside the respirator, it was found that the outside respirator BSF concentrations (25 sets) ranged from 87 to 807 microg/m3, whereas the inside respirator BSF concentrations ranged from 16 to 509 microg/m3. A program protection factor (PPF) for each set of observations was calculated as the ratio of outside to inside air BSF concentrations. The mean PPF was 2.5 with a range of 1.1 to 9.6, and 12 of the 25 measurements (48%) were below 2.0. Although the workers claimed they regularly wore their respirators, the wide range and the low PPF findings suggest that worker behavior and respirator fit may influence the level of protection provided by the respirator.