The development of low-cost research equipment is crucial for enhancing accessibility in scientific research, particularly in the field of respiratory disease transmission. This study presents a novel, customizable cough simulator designed for ad-hoc studies that require precise control over ejection velocity and aerosol size. Constructed from off-the-shelf parts and 3D-printed components, this programmable, piston-driven simulator offers an affordable solution for researchers. Its performance has been validated, demonstrating suitability for evaluating fluid flow and monitoring ejected particles that correspond to the velocities of mouth breathing and coughing. Potential applications for this device include assessments of aerosol ventilation, disinfection, and the efficacy of personal protective equipment, all of which contribute to advancing scientific understanding and public health outcomes.

The size of airborne particles emitted from infected individuals is crucial in the transmission of respiratory viruses. The use of source control devices is essential for interrupting the transmission of exhaled submicron particles, particularly in healthcare settings with high infection risk. This study evaluated the efficacy of five types of source control devices, commonly used in healthcare settings, in mitigating the transmission of exhaled submicron particles (20–210 nm). Total outward leakage (TOL) of these devices was analyzed across different particle sizes, and the TOL mean diameter (TOLMD) was calculated to characterize particle size distribution. The devices tested included N95 filtering facepiece respirators (N95 FFRs), N95 FFRs with an exhalation valve (N95 FFRV), surgical masks (SMs), elastomeric half-mask respirators (EHMRs), and EHMRs with a SM covering the exhalation valve (EHMRSM). The study also examined the effects of faceseal and flowrate on TOL and particle size characteristics. Results indicated that TOL varied with particle size, increasing from 40 to 90 nm before stabilizing. Aerosols larger than 90 nm had significantly higher TOL compared to smaller aerosols. Higher flow rates increased TOL for EHMR and EHMRSM across all particle sizes. Improved faceseal on N95 FFRs and SMs significantly reduced TOL and decreased TOLMD. The study underscored that using well-fitting devices without exhalation valves is crucial for preventing the transmission of exhaled aerosols potentially carrying viruses, in particular for larger particle sizes. This is especially crucial in the absence of proper indoor ventilation and other control measures. © This work was authored as part of the Contributor’s official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.

BACKGROUND: During COVID-19 pandemic, the general public used any face-worn products they could get to overcome the shortage of N95 respirators and surgical masks. These products, often not meeting any standards, raised concerns about their effectiveness in reducing the spread of respiratory viruses. METHODS: This study quantified total outward leakage (TOL) of units from nine face-worn product categories used by members of the general public. A benchtop system was devised to test two units from each category on two different-sized headforms with silicone elastomer skin. Each unit was donned five times per headform. RESULTS: Both face-worn product category and headform size significantly affected TOL (P-Value <0.05). The TOL of tested face-worn products varied from 10% to 58% depending on both model and headform size. Face-worn products donned on the medium headform had a higher mean TOL compared to those donned on the larger headform. CONCLUSIONS: Overall, single-layer cloth masks are the least effective measure for source control due to their highest TOL among the tested face-worn products. Three-layer disposable face masks may be a favorable option for source control among the public. A standard should be developed for face-worn product design and manufacturing to accommodate different facial sizes.

Protective clothing standards, such as test methods published by ASTM International, play an integral role in ensuring the performance of personal protective equipment. The standard tests are not without limitations and are periodically reviewed and often updated. Some tests may not be reflective of in-use conditions. A new test cell was designed using sanitary fixtures to evaluate the effect of glove stretch on barrier performance using fluorescein solution as the challenge agent for enhanced visualization and fluorometer detection. Domed-shaped and flat screens were developed to permit and limit glove stretch within the test cell. The barrier performance of glove swatches was evaluated for both stretched and unstretched states. Latex, nitrile, and vinyl glove models of various thicknesses were evaluated. The tests were conducted following pressure and time parameters specified in ASTM F903, ASTM F1670, and ASTM F1671. Fluorescein solution movement, which may occur through penetration, was measured using a fluorometer. Glove stretch caused a reduction in glove thickness ranging from 16% to 40%. Overall, 21 sample failures were found (16.7%; n = 126) regardless of test condition. Nitrile gloves provided better barrier efficacy with the lowest failure rates (2.38%; 1 failure out of 42) compared to latex (19.4%; 7 failures out of 36) and vinyl gloves (27.1%; 13 failures out of 48). Differences in failure rates between stretched and unstretched gloves were insignificant; however, the latex material showed a 2.5 times increase in failures when stretched compared to unstretched. The new test apparatus was able to differentiate between the barrier performance of different glove materials. The use of a domed screen allowed the gloves to stretch, a condition that better represents the state of gloves when in use. Analysis of samples collected from the glove surface opposite to the exposure may provide a way to assess chemical permeation in addition to penetration.

The objective of this study is to evaluate a prototype local ventilation system (LVS) intended to reduce retail store workers' exposures to aerosols. The evaluation was carried out in a large aerosol test chamber where relatively uniform concentrations of polydisperse sodium chloride and glass-sphere particles were generated to test the system with nano- and micro-size particles. In addition, a cough simulator was constructed to mimic aerosols released by mouth breathing and coughing. Particle reduction efficiencies of the LVS were determined in four different experimental conditions using direct reading instruments and inhalable samplers. The particle reduction efficiency (%) depended on the position beneath the LVS, but the percentage was consistently high at the LVS center as follows: 1) > 98% particle reduction relative to background aerosols, 2) > 97% in the manikin's breathing zone relative to background aerosols, 3) > 97% during mouth breathing and coughing simulation, and 4) > 97% with a plexiglass barrier installation. Lower particle reduction (<70%) was observed when the LVS airflow was disturbed by background ventilation airflow. The lowest particle reduction (<20%) was observed when the manikin was closest to the simulator during coughing.

Surgical N95 filtering facepiece respirators (surgical N95 FFRs) are National Institute for Occupational Safety and Health-approved N95 filtering facepiece respirators (N95 FFRs) cleared by the Food and Drug Administration for resistance to liquid penetration and flammability. A recent study showed that several N95 FFR models performed as well as surgical N95 FFRs in synthetic blood penetration tests that evaluate resistance to penetration by horizontal projection. This aspect, in addition to the influence of other factors on liquid penetration, are not well studied. To address this issue, the effect of liquid volume (1 mL and 2 mL), spray velocity (450 cm/sec and 635 cm/sec), and liquid composition (synthetic blood and diluted synthetic blood) were evaluated. Four types of common protective devices were studied: N95 FFRs, surgical N95 FFRs, surgical masks, and powered air-purifying respirator (PAPR) hoods. For each protective device type, five models were analyzed using a protocol based on the F1862 ASTM International (2017) test method. Reduced liquid volume had a significant effect in only 3 of 20 models. Increased velocity had significantly greater penetration in 9 of 20 models. Diluted synthetic blood had significantly more penetration in 8 of 20 models. This last result was not expected because, in hydrostatic tests, surface tension of the diluted blood would be expected to reduce penetrability; however, across all models tested, data showed that the diluted spray was more penetrable. The study results suggest that fluid composition may be as important as velocity when considering liquid spray penetration. Furthermore, the penetrability of a spray may be inversely related to the penetrability through direct hydrostatic contact.

Personal protective equipment (PPE), such as gowns used in the latest Ebola outbreak in Western Africa, are critical in preventing the spread of deadly diseases. Appropriate test systems and test soils are needed to adequately evaluate PPE. ASTM F903, Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquid, has been used for decades to test fabrics' resistance to liquid penetration. However, this test apparatus requires at least 60 mL of test solutions, is labor intensive, and has problems with leakage around the gaskets. We compared the F903 test apparatus to a modified dot-blot apparatus to evaluate the visual penetration of a blood test soil. A series of commercially available gowns and drapes were tested in each apparatus. Using blood test soil at 2 psi, there was no statistically significant difference between the two methods except for in one gown. By comparing this gown in the ASTM test apparatus with and without a screen, the particular screen selected did not account for the difference between the dot-blot and F903 apparatuses; however, it is conceivable that a particular screen/fabric combination could account for this difference. The modified dot-blot apparatus was evaluated using three different test solutions: blood, vomit, and a labeled protein (goat anti-rabbit immunoglobulin G-horseradish peroxidase [GaR IgG-HRP]) in a blood test soil solution. This testing revealed significant difference in penetration for some of the PPE garments. The modified dot-blot had several large advantages over the ASTM apparatus-over six times less specimen volume and no edge or gasket leakage. In addition, nitrocellulose can be easily incorporated into the modified dot-blot apparatus, enabling the trapping of viruses and proteins that penetrate PPE-thus permitting the use of antibodies to quickly and sensitively detect penetration.

Protective clothing manufacturers routinely test their products for resistance to liquid and viral penetration. Several of the test methods specified by the American Society for Testing and Materials (ASTM) and the International Organization for Standardization (ISO) for penetration testing produce binary results (i.e. pass or fail), deliver imprecise pressure regulation, and do not record the location at which penetration events occur. Instead, our approach measures a continuous variable (time of penetration) during a slow and continuous increase of hydrostatic pressure and retains the location of penetration events. Using a fluorescent dye to enhance visual detection, we evaluate temporal and spatial patterns of penetration events. We then compare the time of liquid penetration with the time of penetration of two bacteriophages (Phi-X174 and MS2). For the fabric tested, the mean viral penetration occurred 0.29 minutes earlier than liquid penetration when solved by logistic regression. The breakthrough time of MS2 was not different from the Phi-X174 bacteriophage. The time of liquid penetration was a latent indicator of the time of viral penetration.

The ASTM F1670 test method, Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Synthetic Blood, was based on research involving transmission of bloodborne pathogens (Hepatitis B, Hepatitis C, and HIV) in the 1980s. The test method details the measurement of synthetic blood penetration through garments. A key parameter affecting penetration is synthetic blood surface tension, which is measured via du Nouy ring tensiometer. However, little is known about the sources of variation impacting surface tension measurements. In this study, the synthetic blood used for ASTM F1670 was evaluated from within the ASTM F903 test apparatus, Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquids, and with two mixing treatments. Measurements were compared against two outside laboratories and with two alternate tensiometric methods (pendant drop and capillary rise). It was found that using the methods specified in the ASTM F1670 test method, surface tension of the synthetic blood was not 40-44 dynes/cm as was expected. The surface tension was initially above 50 dynes/cm and declined to below 40 dynes/cm after 60 minutes. The surface tension within the penetration cell was relatively constant over time, showing that the surface tension measurements outside the penetration cell are not indicative of the surface tension within the apparatus during the test. Shaking the synthetic blood, a mixing procedure detailed in the ASTM F1670 test method, increased the surface tension. The increase was greatest in a container having more airspace. Du Nuoy ring measurements by the National Institute for Occupational Safety and Health compared to external labs were within 15 %. Testing with alternate methods showed that the "open to atmosphere" methods (ring and drop) began lower and declined rapidly when compared to the "closed to atmosphere" method (capillary). Results of this research will help amend the ASTM F1670 standard to better characterize the measurement and handling of synthetic blood used in the ASTM F1670 test and to provide a framework for consideration of test fluid used in future ASTM standards.

The risk of workers' exposure to aerosolized particles has increased with the upsurge in the production of engineered nanomaterials. Currently, a whole-body standard test method for measuring particle penetration through protective clothing ensembles is not available. Those available for respirators neglect the most common challenges to ensembles, because they use active vacuum-based filtration, designed to simulate breathing, rather than the positive forces of wind experienced by workers. Thus, a passive method that measures wind-driven particle penetration through ensemble fabric has been developed and evaluated. The apparatus includes a multidomain magnetic passive aerosol sampler housed in a shrouded penetration cell. Performance evaluation was conducted in a recirculation aerosol wind tunnel using paramagnetic Fe3O4 (i.e., iron (II, III) oxide) particles for the challenge aerosol. The particles were collected on a PVC substrate and quantified using a computer-controlled scanning electron microscope. Particle penetration levels were determined by taking the ratio of the particle number collected on the substrate with a fabric (sample) to that without a fabric (control). Results for each fabric obtained by this passive method were compared to previous results from an automated vacuum-based active fractional efficiency tester (TSI 3160), which used sodium chloride particles as the challenge aerosol. Four nonwoven fabrics with a range of thicknesses, porosities, and air permeabilities were evaluated. Smoke tests and flow modeling showed the passive sampler shroud provided smooth (non-turbulent) air flow along the exterior of the sampler, such that disturbance of flow stream lines and distortion of the particle size distribution were reduced. Differences between the active and passive approaches were as high as 5.5-fold for the fabric with the lowest air permeability (0.00067 m/sec-Pa), suggesting the active method overestimated penetration in dense fabrics because the active method draws air at a constant flow rate regardless of the resistance of the test fabric. The passive method indicated greater sensitivity since penetration decreased in response to the increase in permeability.

Gowns and coveralls are important components of protective ensembles used during the management of known or suspected Ebola patients. In this study, an Elbow Lean Test was used to obtain a visual semi-quantitative measure of the resistance of medical protective garments to the penetration of two bodily fluid simulants. Tests were done on swatches of continuous and discontinuous regions of fabrics cut from five gowns and four coveralls at multiple elbow pressure levels (2 - 44 PSI). Swatches cut from the continuous regions of one gown and two coveralls did not have any strike-through. For discontinuous regions, only the same gown consistently resisted fluid strike-through. As hypothesized, with the exception of one garment, fluid strike-through increased with higher applied elbow pressure, was higher for lower fluid surface tension, and was higher for the discontinuous regions of the protective garments.