Testing of Commercial Masks and Respirators and Cotton Mask Insert Materials using SARS-CoV-2 Virion-Sized Particulates: Comparison of Ideal Aerosol Filtration Efficiency versus Fitted Filtration Efficiency

Hill, Cary; Hull, Matthew S.; MacCuspie, Robert I.

doi:10.1021/acs.nanolett.0c03182

Cited by 80 publications

(114 citation statements)

References 26 publications

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“…A recent study by Sickbert-Bennett et al (71) showed similar PPL results where they evaluated multiple brands of surgical and procedure face masks on one test subject, obtaining mean values of 3.5 and 1.6 respectively. Hill et al's (54) investigation also demonstrated that homemade face coverings provided as-worn filtration efficiencies of 15-40% (PPLs of 1.18 to 1.67). Given that disposable procedure masks and reusable cloth masks are, by simplest definition, a piece of material held in position over the nose and mouth, it may be stated reasonably confidently that a PPL of 2.0-2.5 is likely the upper level of performance that can be anticipated from basic designs of this nature.…”

Section: Discussionmentioning

confidence: 94%

“…4-18 (65) to obtain a PF ≥100 prior to the total inward leakage test being conducted, ii) the design of a FFR provides for a more effective face seal, and iii) the electret filtering material has a much higher filtration efficiency. A recent study by Hill et al (54) showed that qualitatively fitting a KN95 and N95 FFR to a headform resulted in a FFR efficiency of only 0.40, but when the KN95 FFR was sealed to the headform with adhesive, the efficiency increased to 0.967.…”

Section: Discussionmentioning

confidence: 99%

“…Davies et al (47) do not recommend the use of homemade face masks as a method of reducing transmission of infection from aerosols. Hill et al (54) suggest caution when entering areas of high exposure risk wearing homemade face coverings and recommend using masks known to seal to the face. There is certainly merit in these statements due to the potential for a false sense of respiratory safety that may arise from mask use within the public.…”

Section: Discussionmentioning

confidence: 99%

“…Numerous studies have been completed, many recently, discussing filtration efficiency of certified respirators and improvised face coverings and their materials (47)(48)(49)(50)(51)(52)(53)(54)(55). Face coverings are not respirators.…”

mentioning

confidence: 99%

“…Filtration efficiencies for fabrics improved when multiple layers were used and when using a specific combination of different fabrics. The protection performance of face coverings such as disposable procedure masks that do not fit tightly to the face will be dominated by the total inward leakage due to gaps in the fit (48,49) and indeed fit has been demonstrated to play a critical role in the ability of a mask or respirator to protect the wearer from exposure to particulates in the environment (54). The WHO (57) are currently advising a fabric mask composition of at least three layers to take into consideration the possible use of lesser quality and more variable cotton sources such as t-shirts and handkerchiefs, based on testing results cited in their guidance document (50,51).…”

mentioning

confidence: 99%

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N95 respirators, disposable procedure masks and reusable cloth face coverings: total inward leakage and filtration efficiency of materials against aerosol

Duncan

Bodurtha

Naqvi

2020

Preprint

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Humans expel physiological particles continuously through normal respiratory activities such as breathing, talking, coughing and sneezing; a portion of these are aerosol in the size range <5.0 µm. Misconceptions exist on how to best implement face coverings as an effective preventive health measure against potentially infectious respiratory generated aerosol. The aim of this study was to characterise the performance of face coverings against aerosol when worn by individuals, and to quantify the maximum aerosol penetration through the material used in the construction of each mask. The former addresses their use as a means of possible protection against aerosol present in the environment and the latter having relevance to filtration and reducing human generated aerosol from reaching the environment. Face covering performance was assessed by measuring the total inward leakage of aerosol through the mask material and face seal. Aerosol penetration was measured on swatches of material taken from the face covering. An inert polydisperse charge-neutralized NaCl aerosol, with a distribution ranging from 0.023 µm to 5 μm in diameter, was used for the experiments.Total inward leakage tests were completed to assess the protection factor for nine variations of face coverings, including seven reusable cloth masks, of which six were homemade and one was commercially manufactured, and two styles of disposable procedure masks, one with ear loops and one with ties. Our results have shown that face coverings in general provide the wearer only limited protection against aerosol in the environment. All reusable cloth face coverings obtained a practical protection level of less than 2. The performance of the disposable procedure masks varied from 1.7 to 3.6. The mean practical protection level for the nine face coverings was 1.95 with a standard deviation of 0.89. Comparatively, a N95 respirator achieved a protection factor of 166. We have further shown that aerosol readily penetrates through most materials used in face coverings. Aerosol swatch penetration tests were completed on six different fabrics commonly available for reusable homemade face coverings, four different material systems comprised of multiple material types, eight different disposable procedure masks and the filtering material from three different N95 respirators. Maximum aerosol penetration through the six common fabrics varied from 39% to 91%; for systems comprised of multiple types of materials 4% to 23%; for materials used in disposable procedure masks 16% to 80%; and for filtering materials used in N95 respirators 1.0% to 1.9%. We also highlight that with the exception of some of the reusable cloth materials, penetration of particulates at 5 µm diameter, representing the minimum filtration efficiency that could be achieved against droplets, was insignificant; the six common fabrics showed penetration from 1% to 44%; the fabric systems comprised of multiple types of materials <0.9%; the materials used in disposable procedure masks <0.9% to 6%; and the filtering materials used in three different N95 respirators <0.9%. The observations from this study directly demonstrate that face coverings may be optimized by incorporating high filtration efficiency materials in their construction. Face coverings with an enhanced level of filtration would be of benefit in circumstances where SARS-CoV-2 may be present in the aerosol of infected individuals to reduce aerosol emission from respiratory activities penetrating through into the environment.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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N95 respirators, disposable procedure masks and reusable cloth face coverings: total inward leakage and filtration efficiency of materials against aerosol

Duncan

Bodurtha

Naqvi

2020

Preprint

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Masks During Pandemics Caused by Respiratory Pathogens—Evidence and Implications for Action

Cash-Goldwasser,

Reingold,

Luby

et al. 2023

JAMA Netw Open

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ImportanceAs demonstrated by the influenza virus and SARS-CoV-2, viruses spread by the respiratory route can cause deadly pandemics, and face masks can reduce the spread of these pathogens. The effectiveness of responses to future epidemics and pandemics will depend at least in part on whether evidence on masks, including from the COVID-19 pandemic, is utilized.ObservationsWell-designed observational studies have demonstrated the association of mask use with reduced transmission of SARS-CoV-2 in community settings, and rigorous evaluations of mask mandates have found substantial protection. Disagreement about whether face masks reduce the spread of SARS-CoV-2 has been exacerbated by a focus on randomized trials, which are limited in number, scope, and statistical power. Many effective public health policies have never been assessed in randomized clinical trials; such trials are not the gold standard of evidence for the efficacy of all interventions. Masking in the community to reduce the spread of SARS-CoV-2 is supported by robust evidence from diverse settings and populations. Data on the epidemiologic, environmental, and mask design parameters that influence the effectiveness of masking provide insights on when and how masks should be used to prevent transmission.Conclusions and RelevanceDuring the next epidemic or pandemic caused by a respiratory pathogen, decision-makers will need to rely on existing evidence as they implement interventions. High-quality studies have shown that use of face masks in the community is associated with reduced transmission of SARS-CoV-2 and is likely to be an important component of an effective response to a future respiratory threat.

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Effective use of an extraoral vacuum in preventing the dispersal of particulate matter from metal dental materials

Suito

Fujimoto

Goto

et al. 2023

Journal of Occupational Health

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ObjectivesWhen dentists adjust prostheses at the dental chairside, particulate matter (PM) from the dental material is dispersed. Little is known about the effective use of an extraoral vacuum (EOV) in preventing PM dispersal. This study aimed to evaluate the effective use of an EOV in preventing the dispersal of metal PM in dental offices.MethodsThe following experimental conditions were planned: the distance from the EOV to the metallic materials (50, 100, 150, and 200 mm), the horizontal angle between the long axis of the micromotor handpiece and EOV (0°, 45°, and 90°), and the operating time of the EOV (during grinding, during grinding and 1 min thereafter, during grinding and the preceding 1 min, 1 min before and after grinding, and during grinding). Carborundum and silicone points were used for grinding and PM dispersal. Diameters (0.3, 0.5, 1.0, and 3.0 μm) were measured using a laser particle counter.ResultsDepending on the instrument used to grind, there were undetectable PMs of different diameters (Carborundum point: 0.3 and 0.5 μm, Silicone point: 0.3 μm). PMNs were reduced as the distance from the EOV to metal materials decreased. Operating the EOV before grinding along the long axis of the micromotor handpiece was effective in reducing the PMNs.ConclusionPMNs dispersed when grinding metals were effectively reduced by positioning the EOV closer to the grinding surface (within 150 mm) along the long axis of the micromotor handpiece and operating the EOV before grinding.

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Testing of Commercial Masks and Respirators and Cotton Mask Insert Materials using SARS-CoV-2 Virion-Sized Particulates: Comparison of Ideal Aerosol Filtration Efficiency versus Fitted Filtration Efficiency

Cited by 80 publications

References 26 publications

N95 respirators, disposable procedure masks and reusable cloth face coverings: total inward leakage and filtration efficiency of materials against aerosol

N95 respirators, disposable procedure masks and reusable cloth face coverings: total inward leakage and filtration efficiency of materials against aerosol

Masks During Pandemics Caused by Respiratory Pathogens—Evidence and Implications for Action

Effective use of an extraoral vacuum in preventing the dispersal of particulate matter from metal dental materials

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