Face Masks Tested with Desirable Filtering Efficiency Though 70% of the Models Still Need Improvements in Different Aspects

15 December 2020
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Face Masks Tested with Desirable Filtering Efficiency Though 70% of the Models Still Need Improvements in Different Aspects

As the COVID-19 pandemic persists, face mask has become a daily necessity and its protective efficacy is of primary concern to consumers. The Consumer Council tested 30 face mask models and found that for most (29) models, the average Bacterial Filtration Efficiency (BFE) and Particle Filtration Efficiency (PFE) reached 95% or above, which was deemed satisfactory in reaching the Level 1 requirement of the America Society for Testing and Materials (ASTM) F2100 Standard. They should be able to offer basic protection to consumers for daily use. As for the remaining 1 model, test result showed that the average PFE was only 86.64%, which not only did it fail to meet its claimed ASTM Level 2 requirement of 98% or above, but it also missed the Level 1 requirement for providing basic protective efficacy. Moreover, 70% of the models performed poorly in certain testing items. For example, 3 were detected with relatively high level of bioburden, ear straps of about one-third of the models broke in the tension test, and 1 failed to meet the Level 1 requirement in the test of resistance to penetration by synthetic blood. The Council stresses that as face masks are crucial daily necessities against the pandemic, therefore manufacturers should strictly monitor the quality and ensure all important information on the labelling is comprehensive and accurate, so as to ensure the best protection to consumers.

30 models of face masks available in the market were tested. Pricing from around $2.0 to $9.0 on average, 18 (60%) of them claimed to be made in Hong Kong, 8 in mainland China, and others from Taiwan and Vietnam, etc. The test items made reference to the latest revision of Standard Specification for Performance of Materials Used in Medical Face Masks in 2019 which included BFE and PFE, differential pressure (Delta P) and resistance to penetration by synthetic blood, etc of the models, as well as microbiological content and mask harness tension tests in reference to EU EN 14683 Medical face masks - Requirements and test methods and China National Standard GB19083-2010 Technical Requirements for Protective Face Mask for Medical Use.

With reference to the ASTM F2100-19 requirements, the BFE and PFE must be at least 95% for Level 1, and be at least 98% for both Level 2 and Level 3. In both the BFE and the PFE, 5 samples from each model were tested. The test result revealed 29 models had an average BFE and PFE of over 95% while the remaining 1 model labelled as ASTM F2100 Level 2 had an average PFE of just 86.64%. However, 4 models had PFE of all its 5 samples lower than their claims, of which 2 also had BFE lower than their respective claims, falling short of expectation. Taking the model which claimed BFE and PFE of 99% and labelled with ASTM F2100 Level 2 as an example, the actual measured BFE only ranged from 95.8% to 96.5%, and the PFE was even lower, ranging from 84.42% to 87.64%. Its filtration efficiency even failed to achieve the standard of ASTM Level 1. Another model claimed its BFE and PFE to be ≥99%, but the actual measured BFE ranged from 98.1% to 98.6%, and the PFE ranged from 96.15% to 97.32%. Furthermore, the measured PFE or BFE in some samples of 6 models did not meet their respective claims.

The test on resistance to penetration by synthetic blood simulated the splashing of blood or body fluid onto the mask surface to assess the water resistance ability of surgical masks. 32 samples of each model were put to test under corresponding pressure in accordance with their claimed standard level. If more than 3 samples were penetrated by synthetic blood in the lowest pressure of 80 mm Hg, that model would be rated as poor. 70% (21) models had an excellent performance as none of their samples penetrated by synthetic blood. 1 model labelled as anti-dust mask performed poorly as nearly 85% (27) samples were penetrated by synthetic blood under 80 mm Hg pressure test, while for another model labelled as ASTM F2100 Level 3, 11 samples were penetrated by synthetic blood under the pressure corresponding to its standard requirement (160 mm Hg). Nevertheless, the occurrence of being splashed by blood or body fluid is relatively low in daily life.

As wearing face masks could provide protection against infection or transmission of viruses, the hygiene condition of the mask itself is equally important. The EU standard EN 14683:2019 sets the level of the coliform forming unit per gram at less than 30. The test result showed 90% (27) of the models met this standard while the remaining 3 models exceeded this limit with coliform forming unit ranged from 41.7 to more than 159.4. For the model with the highest detectable amount (>159.4CFU/g), its coliform forming unit per gram also exceeded its labelled standard limit of "Bacterial Detection Implement Standard" of the China " Surgical Mask" Standard YY0469-2011 "Non-sterile mask" category which is 100.

As face masks need to be worn for long hours, consumers would also be concerned about comfortability. The test measured the difference in pressure in front of and behind the mask sample in order to evaluate the degree of breathability, which represents wearing comfortability when breathing. Some or all the samples of 4 models were detected a pressure difference of over 5.0 mm H2O/cm2, indicating a lower breathability which may make users feel uncomfortable. For the mask harness tension test, 11 models had at least 1 sample torn apart at below 10N tension and were hence rated as unsatisfactory. Among them, 5 models had even all 4 samples torn apart at below 10N, which may cause wastage and inconvenience to users.

Face masks with BFE 95% or above should be sufficient for providing protection in community settings. However, other than wearing surgical masks, consumers must not neglect other precautionary measures. They should always pay attention to personal and environmental hygiene and take note of the following:

- Wash your hands with soap and water, or alcohol hand rub before putting on a face mask;
- Wear the mask properly. The side with colour and downward folding pattern normally faces out, while the metal or plastic strip faces up;
- The mask should cover your mouth, nose and chin completely;
- After putting on a mask, do not touch it with your hands as it might have been contaminated with bacteria or virus;
- After taking down the mask, throw it in a covered trash can as soon as possible and then clean your hands immediately. Do not place the mask randomly or save it for re-use in your pocket, and do not re-use by cleaning and disinfecting it with water or alcohol.

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