Publications by authors named "Kent C Hofacre"

6 Publications

  • Page 1 of 1

Strap Performance of N95 Filtering Facepiece Respirators After Multiple Decontamination Cycles.

MRS Adv 2020 1;5(56):2881-2888. Epub 2020 Dec 1.

Battelle Memorial Institute, USA.

The Battelle Critical Care Decontamination System™ (CCDS™) decontaminates N95 filtering facepiece respirators (FFRs) using vapor phase hydrogen peroxide (VPHP) for reuse when there is a critical supply shortage. The Battelle CCDS received an Emergency Use Authorization (EUA) from the US Food and Drug Administration (FDA) in March 2020. This research focused on evaluating the mechanical properties of the straps as an indicator of respirator fit. The objective was to characterize the load generated by the straps following up to 20 don/doff and decontamination cycles in Battelle's CCDS. In general, the measured loads at 50 and 100% strains after 20 cycles were similar (±15%) to the as-received controls. Qualitatively, reductions in the load may be associated with loss of elasticity in the straps, potentially reducing the ability to obtain a proper fit. However, small changes in strap elasticity may not affect the ability to obtain a proper fit given the potential for variation in strap length and positioning on the head. Regardless, prior to reusing a N95 respirator, it is important to complete a visual inspection to ensure it is not damaged, malformed, or soiled. If so, it is recommended to discard the respirator and use a different one. Similarly, the respirator should be discarded if the wearer cannot obtain a proper fit during the user seal check.
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http://dx.doi.org/10.1557/adv.2020.378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7790017PMC
December 2020

Fentanyl and carfentanil permeation through commercial disposable gloves.

J Occup Environ Hyg 2020 09 13;17(9):398-407. Epub 2020 Jul 13.

National Institute for Occupational Safety and Health (NIOSH), National Personal Protective Technology Laboratory (NPPTL), Pittsburgh, Pennsylvania.

In 2018, the Centers for Disease Control and Prevention reported that opioid overdose deaths (including fentanyl and carfentanil) comprised 46,802 (69%) of the 67,367 total drug overdose deaths. The opioid overdose epidemic affects Americans not only at home but also in the workplace. First responders may be at risk of opioid exposure during incidents such as vehicle searches and responses to overdose calls. To reduce direct exposure to opioids and other hazardous drugs, first responders rely in part on personal protective equipment (PPE) as their last line of defense. First responders seek guidance from the National Institute for Occupational Safety and Health (NIOSH) regarding appropriate PPE selection for potential opioid exposure. There is limited empirical glove performance data for illicit drugs. Empirical data are needed to validate NIOSH's current recommendations regarding gloves to help prevent exposure to illicit drugs (i.e., powder-free nitrile gloves with a minimum thickness of 5 ± 2 mil [0.127 ± 0.051 millimeters]); however, no industry standard or test method currently exists for specifically evaluating PPE performance against fentanyl and its analogs. To understand the permeation qualities of gloves when challenged against fentanyl and carfentanil solutions, the ASTM International (formerly American Society for Testing and Materials) ASTM D6978-19 standard for chemotherapy drug glove permeation was adapted to test fentanyl and carfentanil hydrochloride solution permeation through twelve disposable glove models, including five models in which the manufacturers claim fentanyl protection. No nitrile glove models showed fentanyl or carfentanil permeation rates above the chemotherapy drug threshold criterion of 0.01 µg/cm/min (i.e., thereby meeting the performance requirement) as calculated using the ASTM D6978-19 standard within the 240-min test. Latex and vinyl glove materials exhibited fentanyl and carfentanil permeation with permeation rates above this threshold. These findings are among the first empirical data to support NIOSH's current opioid glove recommendations and define procedures that could be used to support industry standards for evaluating opioid permeation through air-impermeable PPE materials.
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http://dx.doi.org/10.1080/15459624.2020.1784426DOI Listing
September 2020

Viable viral efficiency of N95 and P100 respirator filters at constant and cyclic flow.

J Occup Environ Hyg 2013 ;10(10):564-72

a U.S. Army Edgewood Chemical Biological Center , Aberdeen Proving Ground , Maryland.

The growing threat of an influenza pandemic presents a unique challenge to healthcare workers, emergency responders, and the civilian population. The Occupational Safety and Health Administration (OSHA) recommends National Institute for Occupational Safety and Health (NIOSH)-approved respirators to provide protection against infectious airborne viruses in various workplace settings. The filtration efficiency of selected NIOSH-approved particulate N95 and P100 filtering facepiece respirators (FFRs) and filter cartridges was investigated against the viable MS2 virus, a non-pathogenic bacteriophage, aerosolized from a liquid suspension. Tests were performed under two cyclic flow conditions (minute volumes of 85 and 135 L/min) and two constant flow rates (85 and 270 L/min). The mean penetrations of viable MS2 through the N95 and P100 FFRs/cartridges were typically less than 2 and 0.03%, respectively, under all flow conditions. All N95 and P100 FFR and cartridge models assessed in this study, therefore, met or exceeded their respective efficiency ratings of 95 and 99.97% against the viable MS2 test aerosol, even under the very high flow conditions. These NIOSH-approved FFRs and particulate respirators equipped with these cartridges can be anticipated to achieve expected levels of protection (consistent with their assigned protection factor) against airborne viral agents, provided that they are properly selected, fitted, worn, and maintained.
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http://dx.doi.org/10.1080/15459624.2013.818228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7196694PMC
March 2014

Reaerosolization of MS2 bacteriophage from an N95 filtering facepiece respirator by simulated coughing.

Ann Occup Hyg 2012 Apr 29;56(3):315-25. Epub 2011 Nov 29.

National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, PA 15236, USA.

The supply of N95 filtering facepiece respirators (FFRs) may not be adequate to match demand during a pandemic outbreak. One possible strategy to maintain supplies in healthcare settings is to extend FFR use for multiple patient encounters; however, contaminated FFRs may serve as a source for the airborne transmission of virus particles. In this study, reaerosolization of virus particles from contaminated FFRs was examined using bacteriophage MS2 as a surrogate for airborne pathogenic viruses. MS2 was applied to FFRs as droplets or droplet nuclei. A simulated cough (370 l min(-1) peak flow) provided reverse airflow through the contaminated FFR. The number and size of the reaerosolized particles were measured using gelatin filters and an Andersen Cascade Impactor (ACI). Two droplet nuclei challenges produced higher percentages of reaerosolized particles (0.21 and 0.08%) than a droplet challenge (<0.0001%). Overall, the ACI-determined size distribution of the reaerosolized particles was larger than the characterized loading virus aerosol. This study demonstrates that only a small percentage of viable MS2 viruses was reaerosolized from FFRs by reverse airflow under the conditions evaluated, suggesting that the risks of exposure due to reaerosolization associated with extended use can be considered negligible for most respiratory viruses. However, risk assessments should be updated as new viruses emerge and better workplace exposure data becomes available.
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http://dx.doi.org/10.1093/annhyg/mer101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7537697PMC
April 2012

N95 and p100 respirator filter efficiency under high constant and cyclic flow.

J Occup Environ Hyg 2009 Jan;6(1):52-61

Battelle Memorial Institute, Columbus, Ohio, USA.

This study investigated the effect of high flow conditions on aerosol penetration and the relationship between penetration at constant and cyclic flow conditions. National Institute for Occupational Safety and Health (NIOSH)-approved N95 and P100 filtering facepiece respirators and cartridges were challenged with inert solid and oil aerosols. A combination of monodisperse aerosol and size-specific aerosol measurement equipment allowed count-based penetration measurement of particles with nominal diameters ranging from 0.02 to 2.9 microm. Three constant flow conditions (85, 270, and 360 L/min) were selected to match the minute, inhalation mean, and inhalation peak flows of the four cyclic flow conditions (40, 85, 115, and 135 L/min) tested. As expected, penetration was found to increase under increased constant and cyclic flow conditions. The most penetrating particle size (MPPS) generally ranged from 0.05 to 0.2 microm for P100 filters and was approximately 0.05 microm for N95 filters. Although penetration increased at the high flow conditions, the MPPS was relatively unaffected by flow. Of the constant flows tested, the flows equivalent to cyclic inhalation mean and peak flows best approximated the penetration measurements of the corresponding cyclic flows.
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http://dx.doi.org/10.1080/15459620802558196DOI Listing
January 2009

Comparison of simulated respirator fit factors using aerosol and vapor challenges.

J Occup Environ Hyg 2004 Jan;1(1):29-38

U.S. Army Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010, USA.

Although not well established, mask leakage measured using submicron aerosol challenges is generally accepted as being representative of vapor challenges. The purpose of this study was to compare simulated respirator fit factors (FFs) measured using vapor challenges to those measured using an aerosol challenge. A full-facepiece respirator was mounted on a headform inside a small enclosure and modified with controlled leaks (laser-drilled orifices) to produce FFs ranging from about 300 to 30,000. A breathing machine was used to simulate breathing conditions of 1.0 L tidal volume and 25 breaths/min. A monodisperse aerosol consisting of 0.72 micron polystyrene latex spheres (PSL) was used for the reference test aerosol, and FFs were measured using a laser aerosol spectrometer. An inert gas, sulfur hexafluoride (SF6), and an organic vapor, isoamyl acetate (IAA), were used as the vapor challenges. The in-mask concentration of SF6 was measured using a gas chromatograph (GC). A GC was also used to quantify in-mask IAA concentration samples actively collected with sorbent tubes. FF measurements made with the PSL aerosol challenge were conducted in sequence with the SF6 and IAA challenges, without disturbing the mask, to yield matched data pairs for regression analysis. FFs measured using the PSL reference aerosol were found to correlate well with those measured with the SF6 (r2 = 0.99) and IAA (r2 = 0.98) vapor challenges. FFs measured using IAA tended to be higher at values below 10,000. The best agreement was observed with the inert gas, SF6. The results of this study suggest that submicron aerosols are suitable as quantitative fit test challenges for assessing the performance of respirators against inert vapors.
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http://dx.doi.org/10.1080/15459620490264454DOI Listing
January 2004