Alternative Face Masks Made of Common Materials for General Public: Fractional Filtration Efficiency and Breathability Perspective

Pei, Chenxing; Ou, Qisheng; Kim, Seong Chan; Chen, Sheng Chieh; Pui, David Y.H.

doi:10.4209/aaqr.2020.07.0423

Cited by 31 publications

(34 citation statements)

References 33 publications

(43 reference statements)

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“…When they travel further in the air, the droplets evaporate to significantly smaller size and the velocity relaxes close to the movement of the surrounding air. In view of the respiratory disease transmission, particles smaller than 10 µm (the size after droplets have reduced in size due to evaporation) pose more risk than larger ones since they are more likely to remain suspended in air 40 , to bypass a face shield, to penetrate through face masks / respirators [41][42][43] , and be inhaled and deposited in the respiratory tract. The residual particle size depends on the size and composition of the original droplets.…”

Section: Ultrasonic Scaler Aerosol Characterizationmentioning

confidence: 99%

Characterization and mitigation of aerosols and splatters from ultrasonic scalers

Placucci

Danielson

et al. 2021

Preprint

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Background: Dental procedures often produce aerosols and splatter which have the potential to transmit pathogens such as SARS-CoV-2. The existing literature is limited. Methods: Aerosols and splatter were generated from an ultrasonic scaling procedure on a dental mannequin and characterized by two optical imaging methods – digital inline holography (DIH) and laser sheet imaging (LSI). Capture efficiencies of various aerosol mitigation devices were evaluated and compared. Results: The ultrasonic scaling procedure generates a wide size range of aerosols up to a few hundred micrometers and occasional large splatter which emit at low velocity (mostly below 3 m/s). Use of a saliva ejector (SE) and high-volume evacuator (HVE) resulted in 63% and 88% of overall reduction respectively while an extraoral local extractor (ELE) resulted in a reduction of 96% at the nominal design flow setting. Conclusions: The study results showed that the use of ELE or HVE significantly reduced aerosol and splatter emission. The use of HVE generally requires an additional person to assist a hygienist, while an ELE can be operated hands-free when a dental hygienist is performing ultrasonic scaling and other operations. Practical Implications: An extraoral local extractor aids in the reduction of aerosols and splatters during ultrasonic scaling procedures, potentially reducing transmission of oral or respiratory pathogens, like SARS-CoV-2. Position and airflow of the device are important to effective aerosol mitigation.

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Section: Ultrasonic Scaler Aerosol Characterizationmentioning

confidence: 99%

Characterization and mitigation of aerosols and splatters from ultrasonic scalers

Placucci

Danielson

et al. 2021

Preprint

Self Cite

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“…Prior works on improvised materials found that common fabrics (sweatshirts, t-shirts, towels and scarfs) can block 10-60% percent of particles in the 0.2-1 µm range (Rengasamy et al 2010) and improves to 90% for the larger particle ranges (>1 µm) due to being in the inertial impaction regime (Konda et al 2020). Other studies have since examined various non-fabric filters, including HVAC filters, vacuum bags, paper towel, and sterilization wraps (300-wt) and found filtrations of between <60-87% at 0.3 um, 5-75% at 0.3 um, 36% at 2.75 um and 95% at 2.75 um, respectively (Pei et al 2020;Rogak et al 2020;Davies et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Filtration efficiency, breathability, and reusability of improvised materials for face masks

Bagheri

Khalaji

Azizi

et al. 2021

Aerosol Science and Technology

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The goal of this study is to evaluate the filtration efficiency and breathability of improvised filtration and commonly available mask materials, as well as to assess their reusability. Materials readily available to the general public such as cotton, fragrance and additive-free dry baby cleaning wipes, and those abundantly available in the hospital setting, such as sterilization wraps, were chosen for testing, amongst others. In the COVID-important 2-5 µm particle range, two-layers of cotton provided filtration efficiency between 34%-66%. Amongst potential filter materials, 300weight sterilization wraps provided approximately 80% filtration efficiency and are readily available in the healthcare setting. The addition of sterilization wrap to cotton fabrics brought the filtration efficiency to above that of the sterilization wrap (80%-90%) at the expense of added pressure drop. Four-layers of dry baby wipes performed very well with a filtration efficiency of 85% and a reasonable pressure drop (1/3 of procedure mask). Since the material is advertised as pure spunlace polypropylene and designed to contact the skin during cleaning, it would appear generally safe as a filter insert. Of improvised filters, polypropylene electrostatic HVAC filters performed the best with filtration efficiencies of >99%, but are not recommended due to the risk of confusion with glass-based HVAC filters and uncertainty regarding trace materials used in the filter. The filtration efficiency of two-layers of cotton fabrics with one-layer of sterilization wrap slightly improved over 10 laundry cycles, while the performance of other non-wovens, like dry baby wipes, degraded more rapidly and should be considered disposable. In summary, we found that two-layers of cotton fabric can provide a comfortable, breathable and reusable option. The addition of a sterilization wrap or four-layers of pure spunlace fragrance free dry baby wipes can significantly improve filtration and block expiratory aerosols at the expense of an added pressure drop.

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“…Whereas some studies use a manikin headform with the full mask (Balazy et al, 2006a,b;He et al, 2013;Bahloul et al, 2014;Shakya et al, 2016;Adhikari et al, 2018;Kumar et al, 2020), other studies cut a portion of the mask/fabric and place it in a filter holder (Eshbaugh et al, 2008;Lin et al, 2017;Konda et al, 2020;Pei et al, 2020;Wang et al, 2020). Many studies use salt, e.g., NaCl (Eshbaugh et al, 2008;He et al, 2014;Lin et al, 2017;Pei et al, 2020), or polystyrene latex (PSL) spherical particles of defined sizes (Qian et al, 1997;Lee et al, 2005;Eshbaugh et al, 2008) to simulate particulate contaminants. The particle concentration used in these experiments varies from hundreds to several tens of thousands of particles per cm 3 (Balazy et al, 2006a,b;Eshbaugh et al, 2008;He et al, 2014;Adhikari et al, 2018).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…These two flow rates are equivalent to respiration at rest (~30 L min -1 ) and during exertion (~85 L min -1 ) (Lee et al, 2005;Bałazy et al, 2006a;He et al, 2014;Pei et al, 2020), considering the average surface area of an N95 (~200 cm 2 ) (Roberge et al, 2010) and the surface area of our test materials. In order to provide a fair comparison of the ability of each material to capture 250 nm PSL particles, all materials were tested at the same flow rate.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Mask Material Filtration Efficiency and Mask Fitting at the Crossroads: Implications during Pandemic Times

Ardon‐Dryer

Warzywoda

Tekin

et al. 2021

Aerosol Air Qual. Res.

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The COVID-19 pandemic triggered the widespread use and need for respirators and face masks for the healthcare workers and public. In this study, several generally available respirators and mask designs were fit tested, and their materials were evaluated for filtration efficiency using 250 nm polystyrene latex particles. Efficiency testing was performed for 2 and 0.5 h at low (2.6 L min-1) and high (7.4 L min-1) airflows, respectively, using ~17.4 cm 2 material area. As expected, all N95 and KN95 respirators passed the fit test, and their materials showed efficiencies >95% for the entire experiment at both airflows. Of the three air filters used in the 3D-printed Montana masks, only the HEPA filter had a filtration efficiency >95% at both airflows. Regardless of the insert material, the Montana mask failed all fit tests. Homemade duckbill masks made of Halyard H600 sterilization wrap and WypAll X80 reusable wipe also failed the fit test, and both filter materials had an average filtration efficiency <95% at high airflows. To explain the filtration efficiency results, the structure and composition of all filter materials were determined using FE-SEM, and IR and Raman spectroscopy. In conclusion, when highly efficient materials are used in masks that do not fit the users properly, the potential of these materials to protect the users from aerosols is compromised. Therefore, the mask design is as important as the filtration efficiency of the mask material.

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Alternative Face Masks Made of Common Materials for General Public: Fractional Filtration Efficiency and Breathability Perspective

Cited by 31 publications

References 33 publications

Characterization and mitigation of aerosols and splatters from ultrasonic scalers

Characterization and mitigation of aerosols and splatters from ultrasonic scalers

Filtration efficiency, breathability, and reusability of improvised materials for face masks

Mask Material Filtration Efficiency and Mask Fitting at the Crossroads: Implications during Pandemic Times

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