key: cord-0963865-afvjhpww
authors: Wang, Wenxia; Chen, Tingting; Li, Zhen; Tan, Qiting; Meng, Zhenbang; Qiu, Hailun; Liu, Xujie; Zheng, Junxia
title: Comparison of filtration efficiency and respiratory resistance of COVID-19 protective masks by multi-national standards
date: 2022-02-11
journal: Am J Infect Control
DOI: 10.1016/j.ajic.2022.02.009
sha: da5afca55b5e1378f2fdd16e9911f88d878316c2
doc_id: 963865
cord_uid: afvjhpww

Background Face masks from worldwide satisfy different standards during the COVID-19 pandemic, which led to the public misunderstanding of the concepts. Methods We systematically evaluated the quality of face masks provided by different companies according to multi-national standards, including EN 149-2001+A1: 2009, GB 2626-2019 and NIOSH 42 CFR Part 84-2019, focusing particularly on the particulate filtration efficiency (PFE) and respiratory resistance performance. Results Three types of masks (planar, folding and cup type masks) were measured based on different standard protocols. The results indicated that the PFE of the mask decreased in sequence of folding mask ≈ cup type mask > planar mask. The respiratory resistance of the masks ranked as follows: cup type mask > folding mask> planar mask. Overall, when PFE was used as the quality indicator, all the masks have a higher chance of meeting criteria of the EN149-2001+A1:2009, followed by the stricter standard set by the GB2626-2019 and NIOSH 42 CFR Part84-2019. Conversely, the respiratory resistance of the masks fulfilled the highest requirement of the EN149-2001+A1:2009 standard, while it is easier to satisfied the standard of GB 2626-2019 and NIOSH 42 CFR Part 84-2019. Conclusions We believe that our study provides effective guidance for customers worldwide to choose proper face masks under different epidemic situations.

also likely witness the global economic repercussions and possible retaliation caused by this pandemic. 3 Therefore, essential preventive measures include social distancing, wearing face masks in public, hand washing and so on have been highly recommended by the WHO to self-protect from possible infection. 4 Due to the main routes of COVID-19 spread caused by the droplet transmission, wearing a mask is one of the most important and popular preventive measures suggested by health institutes and relevant guidelines. 5 Since then, wearing a face mask in daily life activities has become the norm for various population around the world. However, it has been reported that the ubiquitous use and unprecedented demand of face masks worldwide with several times has contributed to the shortage of this product. 6 Besides, the raw materials used for production of face masks is unfit because they do not meet relevant standards or legislation, thus increasing portions of ineffective masks entering the worldwide market. 7, 8 For example, it has been reported that using homemade mask with different materials can also reduce the possible infections to a certain extent. 9, 10 What's more, reuse of mask after disinfection and prolonged use time is also a common phenomenon in many countries where the epidemic is serious and the masks shortage is severe. [11] [12] [13] According to the previous report, the quality of 48.8% of selective brands of masks with a total amount of 160 on the markets is questionable or invalid. 14 Therefore, the quality of some face masks is controversial and necessary to be evaluated with the emergence and exponential spread of COVID-19. Up to now, there are several different national standards worldwide to provide the protocol testing the important factors that determined the quality of the face masks such as the particulate filtration efficiency (PFE), bacterial filtration efficiency (BFE), fluid resistance, breathability and so on. 15 Standards Organization to evaluate the quality of the respiratory. As illustrated in Table 1 , the masks can be divided into three levels (FFP1, FPP2 and FFP3) according to the filtration efficiency. 16 In China, there are many different standards used for various kinds of face masks. The GB2625-2019 standard is the new version that issued in December 31, 2019. The standard specifies the classification and marking, technical requirements, testing methods and identification of self-priming filter anti-particulate respirators (Table 2) . 17 Similarly, respirators in the American market should be certified by the National Institute for Occuppedational Safety and Health (NIOSH). 18 NIOSH test protocol defines N-, R-, and P-series respirators with the filtration efficiency of 95, 99, and 99.97%, respectively, under 42 CFR Part 84. If the masks passed the standards, they can be certified as N95. 19 Overall, different kinds of masks have different scope of applications and standards (Table 3) . However, the customers are misleading when choosing different kinds of face masks defined by various standards.

Herein, we systematically tested the particulate filtration efficiency and respiratory resistance of three types of masks (planar, folding and cup type) provided by different companies according to the above-mentioned standards protocol.

Automated filter tester and breathing resistance tester were used to determine the filtration efficiency and exhalation resistance of face masks under specified conditions. enterprises to grasp the differences between export regional standards and domestic standards, and provide some references for ensuring the quality and safety of mask products and smooth export.

Different types of face masks (Fig 1) were kindly supplied by different companies whose names are omitted to avoid any form of publicity.

The PFE of marks was evaluated by an automated filter tester (TSI 8130A, TSI instruments Inc., America) equipped with aerosol at flow ranges from 1.0 μg/m 3 to 200 μg/m 3 (Fig 2a) . The working principle of the automated filter tester Model 8130A Table 1 , the masks that comply with the European standard EN 149+A1 are suitable for both oily and non-oily particles, but they are also classified into three different levels according to different filtering efficiency. The classification system is divided into three FFP classes, where FFP stands for "Filtering Face Piece". FFP1, FFP2 and FFP3 represent the low, medium and high level of protection, respectively. PFE of masks was measured using an approach based on the requirements of EN 149:2001+A1:2009 (EN 149+A1). 23 Firstly, we need to adjust the filtration efficiency detection system to the detection state, and set the related test parameters. Then connect the filter element to the detection device in an airtight manner with a suitable clamp. Typically, NaCl aerosol was first formed by an aerosol particle generator.

Thereafter, the PFE is tested by measuring penetration of 0.06 μm NaCl aerosols at a flow rate of 95 L/min over a face mask. NaCl penetration measurements were conducted three times for each sample to ensure accuracy. Finally, a mean value of PFE was calculated prior to statistical analysis.

The Standardization Administration of China issued its mandatory national standard GB 2626-2019 Respiratory protection non-powered air-purifying particle respirator in December 31, 2019. This new standard became effective on July 1, 2020 and replaced the previous version of GB . 24 The standard applies to non-powered air-purifying respirator which can help provide respiratory protection against particles (Table 2 ). This mandatory national standard contains the technical requirements including the general requirement, appearance check, filter efficiency, respiratory resistance and so on. In terms of the PFE measurement, the NaCl aerosol with a mean diameter of 0.075 μm was first generated by an aerosol particle generator.

The 2% NaCl aerosol was then loaded into the equipment to measure the PFE of the face masks with a flow rate of 85 L/min.

In 1995, the National Institute for Occupational Safety and Health (NIOSH) published a final rule changing certification requirements for particulate respirators. 19 NIOSH 42 CFR Part 84-2019 is one of the newly approved national standards that containing the requirement of particulate filtration efficiency test. 25 In a standard test, the NaCl salt aerosol with a mean diameter of 0.075 μm was first generated by an aerosol particle generator. The 2% NaCl aerosol was then loaded into the equipment to measure the PFE of the face masks with a flow rate of 85 L/min.

Respiratory resistance data are also essential information to determine the quality of the masks. The respiratory resistance of the masks is tested by inhalation and exhalation. 26 The respiratory resistance of masks was evaluated according to the EN 27 We also use the NIOSH 42 CFR Part 84-2019 test protocol. As shown in Fig 3c, the PFE of the three brands of masks does not meet the standard of the minimum N95 level. Even though the sizes and flow rates of nanoparticles used in both the GB and NIOSH standards are the same, the NIOSH standard starts from 95% filtration efficiency and is divided into three grades: 95%, 99% and 99.97%. 28 Based on the above analysis, we can make the conclusion that the PFE of the masks is different when tested using the procure of different standards (Fig 3d) . Mask #A has the highest PFE using the NIOSH 42 CFR Part 84-2019 protocol, while mask #B and #C have the highest PFE using the GB 2626-2019 protocol. What's more, these planar marks only meet the minimum standards of the above-mentioned protocols, or even not meet the minimum standards. In conclusion, the PFE of the planar masks is #C>#B>#A under these standards. Therefore, it is necessary to take careful consideration of protection level when choosing a planar type mask in the COVID-19 period, because of planar mask has a lower protection level. 29 The PFE of folding masks using different standards

The PFE of the folding masks were also tested based on the three standards (Fig 4d) . In summary, the PFE of the folding masks decreased in sequence of #E>#F>#D, demonstrating the excellent filtration effectiveness of mask #E.

In terms of the cup type masks, the PFE evaluated by different standards is also illustrated in Fig 5. When EN 149-2001+ A1:2009 was used to test the PFE of cup type masks, the PFE of mask #G is 98.12%, which only meet the requirement of FFP2.

However, the PFE of mask #H and #I is 99.23% and 99.48%, respectively, which reach the highest level of FFP3 (Fig 5a) . Additionally, the PFE of mask #G, #H, #I is higher than 95% when tested using the GB 2626-2019 protocol, which all meet the KN95 level (Fig 5b) . Shown in Fig 5c, protocol. It is obvious that the mask #G meet the requirement of N95 while mask #H and #I reach the level of N99. Overall, the PFE of the cup type masks differed slightly when measured using different standard protocols. As illustrated in Fig 5d, 

Respiratory resistance is generally measured by pressure difference or ventilation resistance, which is used to measure breathability and permeability. Generally, the higher the filtration effect, the greater the respiratory resistance. 31 The respiratory resistance of planar masks is measured by using the protocols recorded in the above-mentioned national standards. As shown in Fig 6a~b, 

The respiratory resistance of folding masks is also measured according to the three standards. As illustrated in Fig 7, 

The respiratory resistance of cup type masks was measured based on the procedure of the three national standards. Under the requirement of the EN 149-2001, the inhalation resistance of masks increased from #G to #I (Fig 8a) . As can be seen from Fig 8b, 

In summary, multi-national standards protocols were used to test different kinds of mask products, so as to promote a comprehensive understanding of the test methods in terms of the filtration efficiency and respiratory resistance at home and abroad. The results indicated that no significant difference was noted between the PFE of the folding and cup type mask, but the PFE of the planar mask was significantly lower than the others. However, other studies on the effectiveness of the surgical masks and N95 masks have been revealed that there is no significant difference between the surgical masks and N95 masks. Besides, The NIOSH 42 CFR Part 84-2019 standard had most strict requirement for the PFE of the masks. Therefore, we recommended wearing the NIOSH-Approved respirators (N95, N99, N100, P95, etc.) if someone is caring for COVID-19 patient, at increased risk of severe illness, works a job with a high risk of exposure, traveling, or unable to keep physical distance.

Otherwise, the cheaper planar mask is able to provide a certain level of protection. We believe that this study will help enterprises, testing institutions and the government to better control and supervise product quality and ensure that the general public can chose practical, user-friendly and practical protective mask products.

Financial support from the National Natural Science Foundation of China (NO.

(2020A1515110718) is greatly acknowledged. 

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