How Mask Modifications Impact Efficacy

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With the continued pandemic safety protocols, masks and their various modifications have become commonplace in society. A recent study published in the American Journal of Infection Control looked into the efficacy of different masks against COVID-19.

The most effective modification for improving source control is double masking or using a mask brace. Other effective modifications include knotting and tucking the mask, using earloop toggles, or using an ear loop strap. Ineffective modifications include crossing the earloops or placing a bracket underneath the mask. 

The study tested the effectiveness of masks as source control, which differs from personal protective equipment (“PPE”). Source control prevents the wearer from transmitting aerosols to others, while PPE protects the wearer from exposure. Both cloth and medical masks are for source control, as they are ineffective at providing respiratory protection. In other words, wearing a mask protects those around you, but not yourself. 

The masks used in the study included medical masks and cloth masks of various materials and ply. Double masking was defined as wearing a 3-ply cloth mask over a medical mask. Knotting and tucking was defined as knotting the earloops and tucking the mask loops under the knotted loop. Earloop toggles or adjustable straps were effective when they resulted in increased tension. All masks and other modification devices were purchased online.

The particle collection efficiency was measured for two different brands of medical masks. Without modification, the collection efficiency was 56 per cent and 63 per cent respectively for coughing and 42 per cent and 55 per cent respectively for exhalation. 

When double masking, the collection efficiencies were 85 per cent and 92 per cent when coughing and 92 per cent and 91 per cent when exhaling. With a mask brace overtop, average collection efficiencies were 95 per cent and 99 per cent for coughs and exhalation respectively. 

For cloth masks, efficacy increased with increased ply. The collection efficiency for unmodified masks was 42 per cent for the 2-ply mask, 51 per cent for the 3-ply mask, and 71 per cent for the 4-ply, all for coughs. 

The study was conducted with a simulator that expelled a test aerosol, consisting of potassium chloride and sodium fluorescein aerosol solution, as a source and a breathing simulator six feet away as a recipient. A mask with or without a modification was placed on the source. Then, a particle counter measured the concentration of aerosols at the recipient simulator. 

With the continued prevalence of COVID-19 cases, these methods for scientific evidence on the matter of mask efficacy and the effectiveness of various modifications become increasingly significant.