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Abstract

Background:

Many countries have introduced a compulsory use of community masks for certain public areas during the SARS-CoV-2 pandemic. Different manufacturers offer reusable community masks in large quantities. The efficacy of these masks, however, is unknown.

Method:

We tested available community masks of major manufactures and determined the filtration efficacy using radioactive aerosol particles as well as air resistance with a vacuum measurement.

Results:

Filtration efficacy of the tested reusable community masks ranged from 34.9% ± 1.25% to 88.7% ± 1.18%. Air resistance ranged from 4.3 ± 0.06 to 122.4 ± 0.12 Pa/cm². There was a good correlation between filtration efficacy and air resistance (Pearson correlation 0.938, p < 0.0001).

Conclusions:

Filtration efficacy and air resistance differ significantly between the different community masks, but the two measurements correlate well with each other within the entire test series. For optimal protection, one should select a rather airtight mask. When selecting a mask, the highest level of tolerable air resistance can be used as a selection criterion.

Introduction

Sars-CoV-2 infections were first systematically described in December 2019.^(1,2) Owing to the rapid spread, the WHO classified the infection with the new corona virus on March 12, 2020 as a pandemic.⁽³⁾ As a result, many countries have introduced a mask requirement for the general population. Owing to the supply situation, there should be a prioritization for medical personnel to wear medical mouth/nose protection masks (so-called surgical masks) or filtering face pieces (FFP masks). Medical masks are usually made of nonwoven fabrics. In Europe, they are subject to the requirements of DIN EN 14683: 2019-10. In the United States, these masks are regulated under 21 CFR 878.4040 as class II devices and require premarket notification. Either regulation requires proof of the biocompatibility of the product and the microbiological purity in the packaging as well as a proof of filtration efficacy and breathability (air resistance). Surgical masks, however, were initially designed to prevent the contamination of surgical sites by the operating staff and their effectiveness is measured by the prevention of bacterial contamination caused by the wearer.^(4,5) DIN 14683: 2019-10, therefore, requires a challenge with 3 μm particles containing bacteria and measures growth of bacteria that passed the tested filter membrane. FFP masks and N95 respirators (United States), in contrast, are designed to protect the wearer from inhalation of infectious particles. N95 respirators are regulated in the United States by the FDA, under 21 Code of Federal Regulations (CFR) 878.4040, and Center for Disease Control and Prevention (CDC) National Institute for Occupational Safety and Health (NIOSH) under 42 CFR Part 84. This regulation requires testing with aerosols of 0.3 μm mass median aerodynamic diameter (MMAD). FFP devices are regulated in Europe by DIN EN 149. This norm requires testing with aerosols of 0.6 μm MMAD. Nonmedical masks or so-called community masks are usually made of textile fabrics. These masks are not subject to any norm and just have to ensure that the mouth and nose is covered. Their effectiveness to prevent viral spreading has been proposed by different authors.^(6–11) A field study with >1,600 medical workers in 14 hospitals showed an increased infection rate among wearers of fabric community masks compared with wearers of single-use surgical masks.⁽¹²⁾ However, the community masks used in the study had only a filtration efficacy of 3%. The disadvantage of these masks was explained by the risk of infection of contaminated masks and the lack of filter performance.⁽¹²⁾ A recent publication highlighted the importance of small particles in the transmission process of viral diseases.⁽¹³⁾ Aerosol generation during normal breathing depends on the properties of the airway fluid lining⁽¹⁴⁾ and produces particles of 0.5 μm or smaller.^(15,16) The depth and speed of inhalation influences the amount of particles released, which indicates that the aerosols are formed during inhalation.⁽¹⁷⁾ In knowledge of these data it appears to be important to examine textile community masks for their filter function using small particles. The aim of this study is to investigate the filtration efficacy as well as the breathability (air resistance) of reusable community masks from some large mask manufacturers.

Methods

Reusable (washable) textile community masks from manufacturers who stated that they produce large quantities of masks (>10,000/month) were examined. One mask made from nonreusable FFP fleece was included into the comparative measurements.

The community masks examined and their manufacturer's details are shown in Table 1.

Table 1.

Characteristics of the Investigated Masks

No.	Product name	Material	Layers	Manufacturer
1	Hermko/9920	Polyester 100%	1	Hermann Koch GmbH & Co. KG Dürbheimerstraße 38/1 78604 Rietheim-Weilheim Germany
2	Eterna/676_00_OneS	Cotton 100%	1	ETERNA Mode GmbH Medienstraße 12 94036 Passau Germany
3	Devetex/CPA Maske Typ A	Viscose 72%/ Polyester 28% Multifilament yarn	1	Devetex GmbH Kleinewefersstraße 100 47803 Krefeld Germany
4	HB Protective Wear/HB-06006-77023-001-58	Polyester 98% Carbon 2%	1	HB Protective Wear GmbH & Co.KG Maischeider Straße 19 56584 Thalhausen Germany
5	Wegerich/MM2020-5N	Outside layer: Polyester 100% Inside layer: fleece Polypropylen 100%	3	Schaumstoffe Wegerich GmbH Huberstraße 1 + 2 97084 Würzburg Germany
6	Wollford/Classic Mask 96230	Polyamid 91%/ Elastan 9%	2	Wolford AG Wolfordstr. 1 A-6901 Bregenz Austria
7	Jungfeld/9998990041_0	Cotton 100%	1	stilfaser GmbH Turley-Strasse 8 68167 Mannheim Germany
8	Medima/0112/780–00	Cotton 100%	2	Peters GmbH Bolstr. 32 72459 Albstadt Germany
9	Trigema/20001	Cotton 50% Polyester 50%	2	TRIGEMA Inh. W. Grupp e.K. Josef-Mayer-Str. 31–35 D-72393 Burladingen Germany
10	Mey/39162	Cotton 100%	2	Mey Handels GmbH Auf Steingen 6 72459 Albstadt Germany
11	UYN/UY0700527	Synthetic fiber Texlyte Nano	1	UYN Via Modena, 18 46041 Asola (MN) Italy
12	Armedangels REDAAV 2.0 TC AA	Cotton 50% Polyester 50%	2	Social Fashion Company GmbH Thebäerstr. 17 50823 Köln Germany
13	Van Laack 49.0942.Z50816.999.00	Cotton 100%	3	van Laack GmbH Hennes-Weisweiler-Allee 25 41179 Mönchengladbach Deutschland
14	Cotonea CMS1-KD001_003	Bio-cotton 100%	2	Gebr. Elmer & Zweifel GmbH & Co. KG Auf dem Brühl 1–9 72658 Bempflingen Deutschland
15	Falke Sportive-Dynamic 44802	Outside: knitted Polypropylen 65%, Polyamid 35% Midlayer: Microfilament fleece Inside layer: polyester 70%, polyamid 30%	2	FALKE KGaA Oststraße 5 57392 Schmallenberg Deutschland
16	Falke Classic-Elegant 44801	Outside: knitted Polypropylene 65%, Polyamide 35% Midlayer: microfilament fleece Inside layer: polyester 70%, polyamid 30%	3	FALKE KGaA Oststraße 5 57392 Schmallenberg Deutschland
17	Eterna FFP 672_00_OneS single use	Medical membrane according to EN 149	3	ETERNA Mode GmbH Medienstraße 12 94036 Passau Deutschland

Examination of air resistance

DIN EN 14683: 2019-10 requires a pressure difference of <40 Pa/cm² for the breathability of medical masks when an air flow of 8 L/min is passed over an area of 4.9 cm² of the test membrane. We reproduced the experimental setup described in detail in DIN EN 14683: 2019-10. A pneumotachograph (SOMNOmedics, Randersacker, Germany) was connected on one side to a 4.9 cm² measuring clamping device. On the other side of the clamping device, a pressure sensor (SEN 633; SOMNOmedics) was connected as well as an adjustable suction pump (Fina VAC B 800; Medap, Lenzkirch, Germany). Pressure and flow values were transferred to the local sleep laboratory network through WLAN (SomnoScreen Plus RC easy; SOMNOmedics) and displayed and analyzed by means of the sleep laboratory software (DOMINO^® Software Package; SOMNOmedics). After clamping the respective mask cloth of the respective community mask, the negative pressure was titrated manually to achieve a flow of 133 mL/s (corresponding to 8 L/min). A total of three different masks were measured per brand.

Examination of filtration efficacy

We examined the filtration efficacy using radioactive particles. For this purpose, isotonic saline (0.9%) with 150 MBq 99mTc-diethylenetriamine pentaacetate (DTPA) per mL was nebulized with a Pari LC Sprint Star nebulizer (Pari, Starnberg, Germany) inside an airtight plastic box (Iris 70 L, model no. 135455; IRIS Ohyama, Sendai, Japan) (Fig. 1).

FIG. 1.

(A) Shows how the Michigan lung is connected to port 2 (clamping device of the mask) and 3 (unfiltered reference port). (B) Shows the four connections on the front of the test box (1 = connection of the nebulizer head, 2 = connection to the clamping device, 3 = unfiltered reference port, 4 = port that enables pressure equalization during ventilation through the artificial lungs. The fans inside the boxes produce a homogeneous aerosol distribution after nebulization (C).

After a nebulization time of 20 seconds, the particles were homogeneously distributed and dried for 30 seconds using two fans installed inside the box (Fig. 1C). Water from the particles evaporates within a few seconds (<5 seconds at a relative humidity of 50% and <10 seconds at a relative humidity of 90%).⁽¹⁸⁾ The MMAD of sodium chloride particles emitted from the Pari LC Sprint Star nebulizer is 2.8 μm with a geometric standard deviation of 2 μm. The drying (evaporation) process described earlier thus will result in a particle spectrum of 0.6 ± 0.4 MMAD. The box contains a clamping device for the mask cloth (Fig. 1C) corresponding to DIN EN 14683: 2019-10 with an area of 49 cm² and a second unfiltered reference port. The test box was provided with a total of four 22 mm ventilation hose adapters (ports), which were sealed airtight into the front of the box (Fig. 1B, C). Port 1 is used to connect the Pari nebulizer. Port 2 was connected on the inside to the output of the clamping device and port 3 was connected on the inside to the unfiltered reference connection. From the outside, ports 2 and 3 were ventilated with a two-chamber artificial lung (dual adult test lung model 5600i; Michigan Instruments, Kentwood, MI; Fig. 1A), whose chambers were blocked and thus moved synchronously. Port 4 was only equipped with a filter from the outside and serves for free air circulation during the ventilation of ports 2 and 3. After aerosol nebulization and the evaporation process was completed, the artificial lungs were actuated a total of 10 times with 1 L per chamber to ventilate port 2 (stretched mask cloth) and 3 (unfiltered reference).

To collect the radioactive aerosols, two particle-tight filters (Iso-Gard No. 19212; Teleflex Medical GmbH, Fellbach, Germany) were used at ports 2 and 3 between the box and the artificial lungs. The radioactivity of the filters at ports 2 and 3 were determined using a gamma camera (ECAM Scintron; Medical Imaging Electronics GmbH, Seth, Germany). The background activity was subtracted from the filter activity, the ratio of the measured net counts from ports 2 and 3 corresponds to the filtration efficacy of the mask cloth that was clamped in each case. For each of the community masks listed in Table 1, were examined three different masks.

Statistics

We used the Shapiro–Wilk test to check for normal distribution and Levene's test for equality of variances. For multiple comparison we used analysis of variance. For pairwise comparisons we used a nonpaired two-sided t-test with Bonferroni adjustment for multiple comparisons. A p < 0.05 was considered significant. SPSS (IBM, Armonk, New York) version 26 was used for statistical analysis.

Data sharing policy

The complete data set of all measurements is available on the Mendeley data sharing platform (https://data.mendeley.com/datasets/p7djxzttzc/1).

Results

Filtration efficacy and air resistance are shown in Table 2.

Table 2.

Measurements

No.	Mask	Filtration efficacy (%) ± SD	Air resistance (Pa/cm²) ± SD
1	Hermko 9920	34.9 ± 1.25	4.3 ± 0.06
2	Eterna	37.2 ± 0.85	10.6 ± 0.29
3	Devetex	41.3 ± 2.39	26.4 ± 0.09
4	HB Protective	44.3 ± 1.69	34.0 ± 1.18
5	Wegerich	44.9 ± 0.32	7.6 ± 0.89
6	Wolford	45.3 ± 2.18	23.0 ± 0.77
7	Jungfeld	46.7 ± 1.38	38.7 ± 0.20
8	Medima	46.8 ± 2.60	14.2 ± 0.02
9	Trigema	50.1 ± 0.72	18.4 ± 0.01
10	Mey	55.0 ± 1.67	30.8 ± 0.19
11	UYN	59.7 ± 1.48	60.1 ± 0.31
12	Armedangels	59.8 ± 1.80	16.9 ± 2.60
13	Van Laack	61.3 ± 1.60	52.2 ± 0.83
14	Cotonea	62.5 ± 0.85	74.9 ± 0.89
15	Falke 44802	86.4 ± 0.81	122.4 ± 0.12
16	Falke 44801	88.7 ± 1.18	109.9 ± 0.39
17	Eterna FFP	99.8 ± 0.13	126.7 ± 0.20

Filtration efficacy (%) and air resistance, mean ± SD.

Figure 2 shows differences in the filtration efficacy of the different community masks.

FIG. 2.

Box plot of the measured filtration efficacy. Statistics are shown in Table 3.

Table 3.

p-Values and Confidence Intervals

	Hermko	Eterna	Devetex	HB Protective	Wegerich	Wolford	Jungfeld	Medima	Trigema	Mey	UYN	Armedangels	Van Laack	Cotonea	Falke Sportiv-Dynamic	Falke Classic-Elegant	Eterna FFP
Hermko		NS	p = 0.002	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Eterna	CI −7.1 to −2.6		NS	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Devetex	CI −11.2 to −1.4	CI −8.9 to 0.8		NS	NS	NS	p = 0.013	p = 0.011	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
HB Protec-tive	CI −14.2 to −4.5	CI −12 to −2.2	CI −7.9 to 1.8		NS	NS	NS	NS	p = 0.005	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Weger-ich	CI −14.8 to −5.1	CI −12.6 to −2.8	CI −8.5 to −1.2	CI −5.5 to 4.3		NS	NS	NS	p = 0.021	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Wolford	CI −15.2 to −5.5	CI −13 to −3.2	CI −8.9 to 0.8	CI −5.9 to 3.9	CI −5.3 to 4.5		NS	NS	NS	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Jungfeld	CI −16.6 to −6.9	CI −14.4 to −4.6	CI −10.3 to −0.6	CI −7.3 to 2.4	CI −6.7 to 3.1	CI −6.3 to 3.5		NS	NS	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Medima	CI −16.7 to −7	CI −14.5 to −4.7	CI −10.4 to −0.7	CI −7.4 to 2.4	CI −6.8 to 3	CI −6.4 to 3.4	CI −4.9 to 4.8		NS	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Trigema	CI −20 to −10.3	CI −17.8 to −8.1	CI −13.7 to −4	CI −10.7 to −1	CI −10.1 to −0.4	CI −9.7 to 0.04	CI −8.3 to 1.4	CI −8.2 to 1.5		p = 0.046	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001	p < 0.001
Mey	CI −24 to −15.2	CI −22.7 to −13	CI −18.6 to −8.9	CI −15.6 to −5.9	CI −15 to −5.3	CI −14.6 to −4.9	CI −13.2 to −3.4	CI −13.1 to −3.4	CI −9.8 to −0.03		NS	NS	p = 0.002	p < 0.001	p < 0.001	p < 0.001	p < 0.001
UYN	CI −29.6 to −19.9	CI −27.4 to −17.6	CI −23.3 to −13.6	CI −20.3 to −10.5	CI −19.7 to −9.9	CI −19.3 to −9.5	CI −17.8 ro −8.1	CI −17.8 to −8	CI −14.4 to −4.7	CI −9.5 to 0.2		NS	NS	NS	p < 0.001	p < 0.001	p < 0.001
Armedangels	CI −29.8 to −20	CI −27.4 to −17.7	CI −23.4 to −13.7	CI −20.4 to −10.6	CI −19.7 to −10	CI −19.3 to −9.6	CI −17.9 to −8.2	CI −17.9 to −8.1	CI −14.5 to −4.8	CI −9.6 to 0.1	CI −5 to 4.8		NS	NS	p < 0.001	p < 0.001	p < 0.001
Van Laack	CI −31.2 to −21.5	CI −29 to -19-2	CI −24.9 to −15.2	CI −21.9 to −12.1	CI −21.3 to −11.5	CI −20.9 to −11.1	CI −19.5 to −9.7	CI −19.4 to −9.6	CI −16 to −6.3	CI −11.1 to −1.4	CI −6.5 to 3.3	CI −6.4 to 3.3		NS	p < 0.001	p < 0.001	p < 0.001
Cotonea	CI −32.4 to −22.7	CI −30.1 to −20.4	CI −26.1 to −16.3	CI −23 to −13.3	CI −22.4 to −12.7	CI −22 to −12.3	CI −20.6 to −10.9	CI −20.5 to −10.8	CI −17.2 to −7.5	CI −12.3 to −2.6	CI −7.6 to 2.1	CI −7.6 to 2.2	CI −6 to 3.7		p < 0.001	p < 0.001	p < 0.001
Falke Sportiv-Dynamic	CI −56.3 to −46.6	CI −54.1 to −44.4	CI −50 to −40.3	CI −47 to −37.3	CI −46.4 to −36.7	CI −46 to −36.3	CI −44.6 to −34.9	CI −44.5 to −34.8	CI −41.2 to −31.5	CI −36.3 to −26.6	CI −31.6 to −21.9	CI −31.5 to −21.8	CI −30 to −20.3	CI −28.8 to −19.1		NS	p < 0.001
Falke Classic-Elegant	CI −58.6 to −48.9	CI −56.4 to −46.7	CI −52.3 to −42.6	CI −49.3 to −39.6	CI −48.7 to −39	CI −48.3 to −38.6	CI −46.9 to −37.2	CI −46.8 to −37.1	CI −43.5 to −33.8	CI −38.6 to −28.9	CI −33.9 to −24.2	CI −33.8 to −24.1	CI −32.3 to −22.6	CI −31.1 to −21.4	CI −7.2 to 2.5		p < 0.001
Eterna FFP	CI −69.7 to −60	CI −67.5 to −57.8	CI −63.4 to −53.7	CI −60.4 to −50.7	CI −59.8 to −50.1	CI −59.4 to −49.7	CI −58 to −48.2	CI −57.9 to −48.2	CI −54.6 to −44.8	CI −49.7 to −39.9	CI −45 to −35.3	CI −44.9 to −35.2	CI −43.4 to −33.7	CI −42.2 to −32.5	CI −18.2 to −8.5	CI −15.9 to −6.2

p-Values and CI for pairwise comparisons.

CI, confidence interval.

Figure 3 shows the relationship between filtration efficacy and air resistance.

FIG. 3.

Filtration efficacy in % versus air resistance in Pascal/cm².

Filtration efficacy and air resistance correlate closely (correlation according to Pearson 0.938. p < 0.0001).

Discussion

According to the certification requirements of DIN 14683: 2019-10, none of the tested community masks met the certification requirements (filtration efficacy >99% and air resistance <40 Pa/cm²). Since we used smaller particles as required by the DIN 14683: 2019-10 norm with direct detection of penetrated particles instead of bacterial culture growth, our setup is more rigorous and rather comparable with the DIN EN 149 or NIOSH (42 CFR Part 84) as described in the introduction of this article. However, we felt it was important to use smaller particles that remain airborne for longer periods since these particles are becoming more and more the focus of virus transmission. The filtration efficacy differs more than twofold, the air resistance even by the factor 20. Overall, one can see a very good correlation between filtration efficacy and air resistance. When it comes to filtration efficacy, the number of layers of material does not necessarily seem to be important (Table 1), but rather the quality of the fabric. Davies et al. examined various textile fabrics and nonwoven fabrics and found a wide range of measured filtration efficacies.⁽¹⁹⁾ A recently published study showed that especially the weave density of a fabric influences the filtration efficacy.⁽²⁰⁾ For cotton fabrics this density is determined by the number of threads per inch (TPI). In the latter study, a cotton fabric with 80 TPI had a filtration efficacy of 14%, a cotton fabric with 600 TPI, in contrast, had a filtration efficacy of 98.4%.⁽²⁰⁾ In the case of multilayer fabrics, however, friction between the different layers can generate electrostatic forces, that may positively affect filtration efficacy.⁽²¹⁾

The optimal filter material has, on the one hand, a pore characteristic that prevents the passage of small aerosol particles; on the other hand, the sum of the pore cross section must be large enough to keep the air resistance low. Fulfilling these two requirements in accordance with DIN 14683: 2019-10 is very unlikely to be achieved without the effect of electrostatic forces in the filter membrane.⁽²²⁾ The filter effects of electrostatically charged membranes are reduced during use, whereas the air resistance remains constant. This phenomenon is best explained by a decrease in the electrostatic filter effects.⁽²³⁾ In particular, however, increasing moisture seems to reduce the electrostatic effects.^(24,25)

The latter arises from the exhaled air and of course from the cleaning process with water. That is why membranes with electrostatic properties are deactivated and become ineffective by washing processes and thus are inapplicable for reusable masks.

The direct filter performance of the mask cloth is primarily responsible for the third-party protection component of a mask. It prevents the exhaled aerosol from spreading toward an opposite person. For self-protection, the tightness of the mask on the facial skin plays a decisive role. Investigations could show that a leak at the edge of the mask can reduce the filtration efficacy by up to 60%.⁽²⁰⁾ Mathematical models to assess the likely effectiveness of facemasks on the reproduction number (R) have highlighted the importance of the filtration efficacy.⁽²⁶⁾

The third-party and self-contamination risk increases with the working life of a protective mask^(27,28); therefore, a regular change or a regular cleaning is mandatory. It is assumed that the moisture in the mask cloth as well as the contamination rate of the mask with airborne pathogens increases significantly with longer use of the masks. Blachere et al. called surgical masks and respirators a “personal bioaerosol sampler.”⁽²⁹⁾ Infectious particles from the mask surface could be further spread by contact or re-aerosolization causing self-infection or infection of others.^(27–29)

With regard to the change intervals and hygienic preparation, it is advisable not to exceed a total wearing time of 6 hours.⁽²⁷⁾ The mask should then be disinfected. Disinfectant preparation can be carried out, for example, by washing at >90°C in the washing machine or by boiling the mask for at least 5 minutes. Machine washing in low-temperature programs should be avoided due to the considerable risk of contamination.⁽³⁰⁾ After using the masks and after washing, care should also be taken to ensure that they are completely dry and protected against contamination.

Limitations

There is a huge variety of commercially produced community masks on the market and we were only able to test a small sample. However, we selected manufacturers who claimed to be able to produce large quantities. Owing to shipping restrictions during the corona pandemic our test sample was mainly restricted to brands from the country of the authors.

However, we are convinced that the general principles we explored can be applied to masks of other brands as well. Surface charge is usually not present in liquid (water-based) aerosols. However, we did not use a discharger and cannot fully exclude that filtration efficacy could have been influenced by electrostatic properties of the mask cloth. We used a particle spectrum of 0.6 ± 0.4 μm MMAD. The use of even smaller particles could have resulted in lower filtration efficacies of the community masks we tested.

Conclusion

For community masks a high filtration efficacy goes along with high air resistance and vice versa. In general, the filtration efficacy should be chosen as high as possible, taking into account the tolerance of the air resistance by the wearer. Air resistance of community mask, however, can be substantially higher as allowed for surgical masks.

Further research should focus on the development of reusable mask with electrostatic properties and cleaning procedures that conserve these properties.

Authors' Contributions

D.D. and J.K. designed the study setup and the experiments. L.M., D.P., and D.D. conducted the experiments. L.M. and D.P. extracted and collected the data. D.D. and J.K. analyzed the data. D.D. and F.G. drafted the article. All authors have read the article and agree to the publication.

Footnotes

Author Disclosure Statement

The authors declare they have no competing financial interests.

Funding Information

No funding was received for this article.

Reviewed by:

Gerhard Scheuch

Jens Hohlfield

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Community Masks During the SARS-CoV-2 Pandemic: Filtration Efficacy and Air Resistance

Abstract

Background:

Method:

Results:

Conclusions:

Introduction

Methods

Examination of air resistance

Examination of filtration efficacy

Statistics

Data sharing policy

Results

Discussion

Limitations

Conclusion

Authors' Contributions

Footnotes

Author Disclosure Statement

Funding Information

References