Protective facial masks worn by many medical practitioners not safe, study finds

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A nurse puts on PPE before tending to a Covid-19 patient.
A nurse puts on PPE before tending to a Covid-19 patient.
Thomas Lohnes/Getty Images
  • Protective facial masks used by many medical practitioners are not safe.
  • A study conducted on 12 brands of KN95 masks by the University of Cape Town revealed none of them met stipulated safety requirements.
  • It found they did not provide adequate protection from dangerous respiratory pathogens, including mycobacterium tuberculosis and SARS-CoV-2 that causes Covid-19.


 Protective facial masks used by many healthcare practitioners are not safe.

A study conducted on 36 masks, from 12 KN95 brands, by a team of medical experts from the University of Cape Town found none of them met stipulated safety requirements.

Eight of the brands had identifiable manufacturer details, only one was on the National Institute for Occupational Safety and Health (NIOSH) approved list, and the mask type and manufacturing details were printed on only two of the 12 brands as per NIOSH and EU regulatory requirements.

The number of individual mask layers of 12 different brands varied between three and only one of the 36 KN95 masks passed the seal test, even after the modification of the ear loop tension using different methods.

Fifteen masks, which passed the seal test, failed qualitative fit testing and of the eight masks tested, only four passed the filtration efficacy testing.

In a report released by the researchers, they stated the masks did not provide adequate protection from dangerous respiratory pathogens, including mycobacterium tuberculosis and SARS-CoV-2 that causes Covid-19.

READ | In-depth: The tangled web of medical device regulation in SA

"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," read the report authored by Keertan Dheda.

Key strengths of the research included a testing protocol incorporating seal, fit testing and measuring the filtration integrity of the masks.

"To our knowledge, this is the only published study that has evaluated all these parameters and dimensions across a range of different KN95 brands and involving 36 different KN95 masks. However, the study has several limitations.

"We sampled only a limited number of masks, and only those accessible to us. However, some masks that were sent to us came from outside the Western Cape area, although most were already being used in hospitals in the Western Cape or in other regions of SA.

"Secondly, we only performed testing on a limited number of participants. Nevertheless, we conducted several different types of testing and included modifications to try to improve the facial seal, and further increasing participant sample size is unlikely to have changed our results," said Dheda.

Researchers did not measure and categorise facial dimensions.

"Finally, although we tested the filter integrity of the masks, this may not equate to the type of testing using commercially standardised equipment that may be performed by certified bodies such as the NIOSH.

"Nevertheless, we did use similar flow rates, a commercially available particle counter, a surgical mask as a negative control and certified KN95 masks as positive controls to validate our findings. We are in the process of validating our low-cost testing rig against a standardised commercially available system such as the TSI 8130A Automated Filter Tester (TSI, USA)," Dheda added.


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