All the Chinese KN95 masks, widely imported into South Africa to counter the COVID-19 pandemic, tested in a University of Cape Town study, failed to provide the protection provided by the ‘gold standard’ N95 mask, reports MedicalBrief.
The study, published in the SA Medical Journal, found that none of the 12 brands of KN95 masks tested (comprising 36 masks) met stipulated safety requirements known to prevent infection by dangerous respiratory pathogens including (tuberculosis) and SARS-CoV-2.
The study, notes that the N95 mask (FFP2 in Europe) is the primary mode of respiratory protection in most parts of the world because of the high regulatory standards to which it is manufactured. However, owing to the severe global shortage of N95 masks during the COVID-19 pandemic, there has been a growing demand for N95-like FFRs. The most commonly available substitute for the N95 mask has been the KN95 mask, which is mainly manufactured in China to the GB2626-2006 standard, and which is considered equivalent to the N95
by the US Food And Drug Administration (FDA) following Emergency Use Authorisation based on testing of filtration efficacy of the mask material.
“The manufacture of N95-like masks remains highly regulated in order to ensure that they filter out at least 95% of penetrating aerosol particles ≥0.3 µm in diameter, fit tightly to maximise the passage of inhaled air through the filter fabric of the mask, and have low inhalational resistance to minimise breathing difficulty. There has been a growing concern about the quality of the circulating supplies of N95-like masks
in many parts of the world, including the circulation of counterfeit masks.
The study concludes” “Our results are concerning because none of the KN95 masks tested met stipulated safety requirements, including passing the seal test and the qualitative fit test, and mask material filtration efficacy. We recommend stronger oversight by regulatory agencies such as the SA Health Products Regulatory Authority to enforce recently published amended regulations and extend this to manufacturers and distributors.
“We also recommend that fit testing be enforced, and that institutional capacity throughout the country be improved for qualitative fit and mask filter material efficacy testing. We would further recommend that the national pre-distribution evaluation protocols and regulations should include fit testing in a range of participants in additional to mask material filter integrity testing. Indeed, in the single NIOSH-approved KN95 mask that we evaluated, the filtration testing requirements but not the fit testing ones were met.
“It would be useful to have a local website (perhaps under the auspices of a regulatory agency) that can vet masks that have already been tested and are deemed to be safe for use. Existing organisations and websites that publish tested and approved KN95 masks include the NIOSH Certified Equipment List or the NIOSH Trusted Source, and the FDA Appendix A or Exhibit 1.
“The Chinese regulatory agency for medical devices also provides details about National Medical Products Administration certification. Such sites also highlight clues to counterfeit masks that do not meet safety requirements, including lack of manufacturer and distributor information, the presence of ear loops, perforation in the mask material, lack of labelling on the mask certifying that it is approved, and embossing on KN95s that exposes the underlying filter layer.
“Our findings will have relevance even after the COVID-19 epidemic has passed, because existing KN95 stockpiles may be given to healthcare workers to prevent infection by M. tuberculosis. We would recommend against this practice, given the failure of these masks to meet stipulated safety requirements.”
KN95 filtering facepiece respirators distributed in South Africa fail safety testing protocols
L Mottay, J le Roux, R Perumal, A Esmail, L Timm, S Sivarasu, K Dheda
SA Medical Journal, December 2020
Given the global shortage of N95 filtering facepiece respirators (FFP2 in Europe) during the COVID-19 pandemic, KN95 masks (Chinese equivalent of the N95 and FFP2) were imported and distributed in South Africa (SA). However, there are hardly any published independent safety data on KN95 masks.
To evaluate the seal, fit and filtration efficiency of several brands of KN95 masks marketed for widespread use in SA healthcare facilities, using standardised testing protocols.
The verifiability of manufacturer and technical details was first ascertained, followed by evaluation of the number of layers comprising the mask material. The testing protocol involved a directly observed positive and negative pressure user seal check, which if passed was followed by qualitative fit testing (sodium saccharin) in healthy laboratory or healthcare workers. Quantitative fit testing (3M) was used to validate the qualitative fit testing method. The filtration efficacy and integrity of the mask filter material were evaluated using a particle counter-based testing rig utilising aerosolised saline (expressed as filtration efficacy of 0.3 µm particles). Halyard FLUIDSHIELD 3 N95 and 3M 1860 N95 masks were used as controls.
Results. Twelve KN95 mask brands (total of 36 masks) were evaluated in 7 participants. The mask type and manufacturing details were printed on only 2/12 brands (17%) as per National Institute of Occupational Safety and Health and European Union regulatory requirements. There was considerable variability in the number of KN95 mask layers (between 3 and 6 layers in the 12 brands evaluated). The seal check pass rate was significantly lower in KN95 compared with N95 masks (1/36 (3%) v. 12/12 (100%); p<0.0001). Modification of the KN95 ear-loop tension using head straps or staples, or improving the facial seal using Micropore 3M tape, enhanced seal test performance in 15/36 KN95 masks evaluated (42%). However, none of these 15 passed downstream qualitative fit testing compared with the control N95 masks (0/15 v. 12/12; p<0.0001). Only 4/8 (50%) of the KN95 brands tested passed the minimum filtration requirements for an N95 mask (suboptimal KN95 filtration efficacy varied from 12% to 78%, compared with 56% for a surgical mask and >99% for the N95 masks at the 0.3 µm particle size).
The KN95 masks tested failed the stipulated safety thresholds associated with protection of healthcare workers against airborne pathogens such as SARS-CoV-2. These preliminary data have implications for the regulation of masks and their distribution to healthcare workers and facilities in SA.
Full text in SA Medical Journal (open access)