To be effective, a negative-pressure, air-purifying, particulate-removing, half-facepiece respirator (particulate respirator) must form a good seal against the wearer’s face. This fact has long been recognized by those in the respiratory protection n community. As one historical example, in 1911, German investigators conducted studies on fit (Brown 1937). However, the current National Institute for Occupational Health and Safety (NIOSH) respirator approval program does not evaluate particulate respirator fit characteristics. Therefore, it is difficult to predict which particulate respirator model will be the best fit in a particular population. Having particulate respirators with good fit characteristics is extremely important today. With the resurgence of tuberculosis (TB) in the United States in the 1990s, the use of particulate respirators in healthcare has increased due to surgical masks only providing barrier protection against droplets that include large respiratory particles. Most surgical masks lack an adequate face seal and do not effectively filter small particles from the air or aerosols, allowing for leakage around the mask and subsequent exposure (Umer et al. 2020). Therefore, surgical masks do not provide adequate protection against infectious respiratory diseases since they are transmitted via droplets and aerosols. With this increased use of particulate respirators in healthcare, supplies of particulate respirators, including N95 filtering facepiece respirators (FFRs), can become depleted during a pandemic or widespread outbreak of infectious respiratory illnesses (Institute of Medicine 2006). However, previous shortages pale in comparison to those caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. The resulting respirator shortage left doctors, nurses, and other frontline workers dangerously ill-equipped to care for COVID-19 patients while protecting themselves from being infected with SARS-CoV-2. The shortages were so severe that even with the availability of hundreds of NIOSH-approved particulate respirator models, under an emergency use authorization, the U.S. Food and Drug Administration (FDA) allowed certain non-NIOSH approved particulate respirators to be used in healthcare for protection against COVID-19 (FDA 2020). Many employers had to buy whatever respirators they could find, resulting in healthcare workers having to wear particulate respirators with which they were unfamiliar. With the need to wear these respirators immediately to care for COVID-19 patients, some healthcare workers may have increased their risk of exposure and infection by wearing respirators with poor fit characteristics. In addition to healthcare workers, particulate respirator wearers in other industries may be at risk from overexposure to various contaminants. A 2001 survey of over 40,000 establishments designed to represent all private-sector establishments revealed that only about 57% of those requiring the use of tight-fitting facepiece respirators performed fit testing (BLS/ NIOSH 2003). Having particulate respirators that meet a standard such as the new ASTM F3407-20 Standard Test Method for Respirator Fit Capability (RFC) for Negative-Pressure Half-Facepiece Particulate Respirators would reduce the number of employees who may be overexposed due to wearing a particulate respirator with poor fit characteristics.

National Institute for Occupational Safety and Health (NIOSH)-approved respirators are required by the Occupational Safety and Health Administration (OSHA) when personal respiratory protection is used in US occupational settings. During the COVID-19 pandemic, the demand for NIOSH-approved N95 filtering facepiece respirators overwhelmed the available supply. To supplement the national inventory of N95 respirators, contingency and crisis capacity strategies were implemented and incorporated a component that endorsed the use of non-NIOSH-approved respiratory protective devices that conformed to select international standards. The development and execution of this strategy required the collaborative effort of numerous agencies. The Food and Drug Administration temporarily authorized non-NIOSH-approved international respiratory protective devices through an emergency use authorization, OSHA relaxed their enforcement guidance concerning their use in US workplaces, and NIOSH initiated a supplemental performance assessment process to verify the quality of international devices. NIOSH testing revealed that many of the non-NIOSH-approved respiratory protective devices had filtration efficiencies below 95% and substantial inconsistencies in filtration performance. This article reports the results of the NIOSH testing to date and discusses how it has contributed to continuous improvement of the crisis strategy of temporarily permitting the use of non-NIOSH-approved respirators in US occupational settings during the COVID-19 pandemic.

This study aimed to quantify the variability between different anthropometric panels in determining the inward leakage (IL) of N95 filtering facepiece respirators (FFRs), and elastomeric half-mask respirators (EHRs). We enrolled 144 experienced and non-experienced users as subjects in this study. Each subject was assigned five randomly selected FFRs and five EHRs, and performed quantitative fit tests to measure IL. Based on the NIOSH bivariate fit test panel, we randomly sampled 10,000 pairs of anthropometric 35 and 25 member panels without replacement from the 144 study subjects. For each pair of the sampled panels, a Chi-Square test was used to test the hypothesis that the passing rates for the two panels were not different. The probability of passing the IL test for each respirator was also determined from the 20,000 panels and by using binomial calculation. We also randomly sampled 500,000 panels with replacement to estimate the coefficient of variation (CV) for inter-panel variability. For both 35 and 25 member panels, the probability that passing rates were not significantly different between two randomly sampled pairs of panels was higher than 95% for all respirators. All efficient (passing rate ≥80%) and inefficient (passing rate ≤60%) respirators yielded consistent results (probability >90%) for two randomly sampled panels. Somewhat efficient respirators (passing rate between 60% and 80%) yielded inconsistent results. The passing probabilities and error rates were found to be significantly different between the simulation and binomial calculation. The CV for the 35 member panel was 16.7%, which was slightly lower than that for the 25 member panel (19.8%). Our results suggested that IL inter-panel variability exists, but is relatively small. The variability may be affected by passing level and passing rate. Facial dimension based fit test panel stratification was also found to have significant impact on inter-panel variability, i.e., it can reduce alpha and beta errors, and inter-panel variability.

Inter-panel variability has never been investigated. The objective of this study was to determine the variability between different anthropometric panels used to determine the inward leakage (IL) of N95 filtering facepiece respirators (FFRs) and elastomeric half-mask respirators (EHRs). A total of 144 subjects, who were both experienced and non-experienced N95 FFR users, were recruited. Five N95 FFRs and five N95 EHRs were randomly selected from among those models tested previously in our laboratory. The PortaCount--> Pro+ (without N95-Companion) was used to measure IL of the ambient particles with a detectable size range of 0.02 to 1 microm. The Occupational Safety and Health Administration (OSHA) standard fit test exercises were used for this study. IL test were performed for each subject using each of the 10 respirators. Each respirator/subject combination was tested in duplicate, resulting in a total 20 IL tests for each subject. Three 35-member panels were randomly selected without replacement from the 144 study subjects stratified by the National Institute for Occupational Safety and Health (NIOSH) bivariate panel cell for conducting statistical analyses. The geometric mean (GM) IL values for all 10 studied respirators were not significantly different among the three randomly selected 35-member panels. Passing rate was not significantly different among the three panels for all respirators combined or by each model. This was true for all IL pass/fail levels of 1%, 2% and 5%. Using 26 or more subjects to pass the IL test, all three panels had consistent passing/failing results for pass/fail levels of 1% and 5%. Some disagreement was observed for the 2% pass/fail level. Inter-panel variability exists, but it is small relative to the other sources of variation in fit testing data. The concern about inter-panel variability and other types of variability can be alleviated by properly selecting: pass/fail level (IL 1% to 5%); panel size (e.g., 25 or 35); and minimum number of subjects required to pass (e.g., 26 of 35 or 23 of 35).

Direct-reading organic vapor monitors are often used to measure volatile organic compound concentrations in complex chemical gas mixtures. However, there is a paucity of data on the impact of multiple gases on monitor performance, even though it is known that monitor sensitivity may vary by chemical. This study investigated the effects of interferents on the performance of the MIRAN SapphIRe Portable Ambient Air Analyzer (SAP) and Century Portable Toxic Vapor Analyzer (TVA-1000) when sampling a specific agent of interest (cyclohexane). The TVA-1000 contained a dual detector: a photoionization detector (PID) and a flame ionization detector (FID). Three devices of each monitor were challenged with different combinations of cyclohexane and potential interferent vapors (hexane, methyl ethyl ketone, trichloroethylene, and toluene) at 21°C and 90% relative humidity (RH), an extreme environmental condition. Five replicates at four target concentrations were tested: 30, 150, 300, and 475 ppm. Multiple proportions of cyclohexane to interferent enabled the determination of the interferent effect on monitor performance. The monitor concentrations were compared to reference concentrations measured using NIOSH Method 1500. Three scenarios were investigated: no response factor, cyclohexane response factor, and weighted-mixed response factor applied. False negatives occurred more frequently for PID (21.1%), followed by FID (4.8%) and SAP (0.2%). Measurements from all monitors generally had a positive bias compared to the reference measurements. Some monitor measurements exceeded twice the reference concentrations: PID (36.8%), SAP (19.8%), and FID (6.3%). Evaluation of the 95% confidence intervals indicated that performance of all monitors varied by concentration. In addition, the performance of the PID and SAP varied by presence of an interfering compound, especially toluene and hexane for the PID and trichloroethylene for the SAP. Variability and bias associated with all these monitors preclude supplanting traditional sorbent-based tube methods for measuring volatile organic compounds (VOCs), especially for compliance monitoring. Industrial hygienists need to use care when using any of the three monitor detection types to measure the concentration of unknown chemical mixtures. Monitor performance is affected by the presence of interferents. Application of manufacturer recommended response factors may not adequately scale measurements to minimize monitor bias when compared to standard reference methods. Users should calibrate their monitors to a known reference method prior to use, if possible. Each of the monitors has its own limitations, which should be considered to ensure quality measurements are reported.

The performance of two direct-reading organic vapor monitors (monitors) when calibrated at different environmental conditions was compared with charcoal tube results. Three MIRAN SapphIRe portable ambient air analyzers (SAP) and three Century portable toxic vapor analyzers (TVAs) were evaluated. Prior to sampling, the monitors were calibrated per the manufacturer's instructions using methane for the TVA flame ionization detector (FID) and isobutylene for the photoionization detector (PID), whereas the SapphIRe instruments were zeroed and the instrument's manufacturer-supplied library was used. For the first series of tests (Part 1Same condition), the monitors were calibrated under the same environmental conditions as those present during sampling. They were then challenged with four cyclohexane concentrations (30, 150, 300, and 475 ppm) under two extreme environmental conditions: 5 degrees C and 30% relative humidity (RH) (same/cold) and 38 degrees C and 90% RH (same/hot). For the second series of tests (Part 2Different condition), the monitors were calibrated at approximately normal indoor environmental conditions (21 degrees C and 50% RH) and sampled at extreme environmental conditions (different/cold and different/hot). The monitor readings from the two methods were compared with the actual cyclohexane concentration determined from charcoal tubes using ratios and root mean square errors. A number of monitor failures, both below detection limit values in the presence of a known challenge concentration and erroneously high measurements, occurred in each part: same condition 20.7% (149/720) and different condition 42.4% (305/720), with a majority of the failures (>78%) during the hot and humid conditions. All monitors performed best at the same/cold, followed by the same/hot, in terms of closeness to the reference standard method and low within-monitor variability. The ranked choice of monitors for same/cold is PID > SAP > FID; for different/cold FID > PID > SAP; for same/hot SAP > PID > FID; and for different/hot PID > SAP (FID not included due to 100% failure rate). Implications: Direct-reading organic vapor monitors are used for assessing the concentrations of volatile organic compounds in the air at varying environmental conditions. Typical calibration is performed at laboratory temperature and pressure. The monitors may be used in atmospheres that differ from that during calibration. An understanding of the effect of calibration environment on monitor performance may provide valuable information on the reliability and appropriateness of certain monitor types for industrial hygienists, emergency responders, and exposure assessment practitioners. Results of the study indicate monitor calibration should be performed at the same environmental conditions as sampling.

The question of whether influenza is transmitted to a significant degree by aerosols remains controversial, in part, because little is known about the quantity and size of potentially infectious airborne particles produced by people with influenza. In this study, the size and amount of aerosol particles produced by nine subjects during coughing were measured while they had influenza and after they had recovered, using a laser aerosol particle spectrometer with a size range of 0.35 to 10 mcm. Individuals with influenza produce a significantly greater volume of aerosol when ill compared with afterward (p = 0.0143). When the patients had influenza, their average cough aerosol volume was 38.3 picoliters (pL) of particles per cough (SD 43.7); after patients recovered, the average volume was 26.4 pL per cough (SD 45.6). The number of particles produced per cough was also higher when subjects had influenza (average 75,400 particles/cough, SD 97,300) compared with afterward (average 52,200, SD 98,600), although the difference did not reach statistical significance (p = 0.1042). The average number of particles expelled per cough varied widely from patient to patient, ranging from 900 to 302,200 particles/cough while subjects had influenza and 1100 to 308,600 particles/cough after recovery. When the subjects had influenza, an average of 63% of each subject's cough aerosol particle volume in the detection range was in the respirable size fraction (SD 22%), indicating that these particles could reach the alveolar region of the lungs if inhaled by another person. This enhancement in aerosol generation during illness may play an important role in influenza transmission and suggests that a better understanding of this phenomenon is needed to predict the production and dissemination of influenza-laden aerosols by people infected with this virus. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resources: a PDF file of demographic information, influenza test results, and volume and peak flow rate during each cough and a PDF file containing number and size of aerosol particles produced.]

The National Institute for Occupational Safety and Health (NIOSH) research on direct-reading instruments (DRIs) needed an instantaneous sampling method to provide independent confirmation of the concentrations of chemical warfare agent (CWA) simulants. It was determined that evacuated canisters would be the method of choice. There is no method specifically validated for volatile organic compounds (VOCs) in the NIOSH Manual of Analytical Methods. The purpose of this study was to validate an evacuated canister method for sampling seven specific VOCs that can be used as a simulant for CWA agents (cyclohexane) or influence the DRI measurement of CWA agents (acetone, chloroform, methylene chloride, methyl ethyl ketone, hexane, and carbon tetrachloride [CCl(4)]). The method used 6-L evacuated stainless-steel fused silica-lined canisters to sample the atmosphere containing VOCs. The contents of the canisters were then introduced into an autosampler/preconcentrator using a microscale purge and trap (MPT) method. The MPT method trapped and concentrated the VOCs in the air sample and removed most of the carbon dioxide and water vapor. After preconcentration, the samples were analyzed using a gas chromatograph with a mass selective detector. The method was tested, evaluated, and validated using the NIOSH recommended guidelines. The evaluation consisted of determining the optimum concentration range for the method; the sample stability over 30 days; and the accuracy, precision, and bias of the method. This method meets the NIOSH guidelines for six of the seven compounds (excluding acetone) tested in the range of 2.3-50 parts per billion (ppb), making it suitable for sampling of these VOCs at the ppb level.

Direct-reading organic vapor monitors (DROVMs) are widely used by industrial hygienists and emergency responders as survey tools for the assessment of volatile organic compounds (VOCs) in occupational or emergency response settings. Although these monitors provide real-time information for expedient decision making, their utility in determining compliance with specific exposure limits is not well established. In addition, other VOCs that may be present in the same environment can act as interferents and adversely affect performance. This study assessed the effect of an interferent (hexane) on the performance of two representative commercially available monitors when measuring cyclohexane. The instrument readings were compared with concentrations measured with sorbent tubes, a standard compliance monitoring technique. Infrared-based concentration measurements were more precise at the two middle challenge concentrations (144 and 289 ppm), indicating a shift in instrument precision at the low and high end of the recommended operating range. Both photoionization detection and infrared-based concentration measurements were affected by the presence and amount of hexane in the test atmosphere. Emergency response personnel and industrial hygienists should be aware of the limitations of DROVMs in the assessment of hazardous situations involving VOCs.

Direct-reading methods (DRMs) are valuable tools for detecting and measuring worker exposure to inhalation hazards. A DRM can be either a device or instrument capable of measuring gases and vapors and aerosols such as dusts, fumes, and mists without manipulation of the sample by the user or sending the sample to an offsite laboratory. Devices are those DRMs that are simple, single point in time measurement of exposure. Instruments are DRMs that contain a sampling system, signal-processing electronics, a display system, and a detector. This manuscript will describe the DRMs which may be used to evaluate worker exposure to gases, vapors, and aerosols. The manuscript will also discuss factors to consider when selecting a DRM and recent developments and events related to DRMs.

Two independent modifications were made to one of two identical side-by-side filter banks for a large air-handler: ( 1) new filter holders, intended to provide a better seal and ( 2) ultraviolet germicidal irradiation (UVGI) lamps, intended to control microbiological growth. Total system efficiency testing with optical particle counters was performed to determine the effectiveness of the new filter holders. The efficacy of the UVGI lamps was determined through biological surface and air sampling. Results indicated that the side with the new filter holders was about 3.4% more efficient per year during the 22-month sampling period, whereas the coil chamber with the UVGI lamps had less biological contamination than the corresponding control chamber for over 75% of the sampling days.