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. 2020 Sep 22;10(9):e039424.
doi: 10.1136/bmjopen-2020-039424.

Ability of fabric face mask materials to filter ultrafine particles at coughing velocity

Eugenia O'Kelly  1 , Sophia Pirog  2 , James Ward  3 , P John Clarkson  4
Affiliations

Ability of fabric face mask materials to filter ultrafine particles at coughing velocity

Eugenia O'Kelly et al. BMJ Open. .

Abstract

Objective: We examined the ability of fabrics which might be used to create home-made face masks to filter out ultrafine (0.02-0.1 µm) particles at the velocity of adult human coughing.

Methods: Twenty commonly available fabrics and materials were evaluated for their ability to reduce air concentrations of ultrafine particles at coughing face velocities. Further assessment was made on the filtration ability of selected fabrics while damp and of fabric combinations which might be used to construct home-made masks.

Results: Single fabric layers blocked a range of ultrafine particles. When fabrics were layered, a higher percentage of ultrafine particles were filtered. The average filtration efficiency of single layer fabrics and of layered combination was found to be 35% and 45%, respectively. Non-woven fusible interfacing, when combined with other fabrics, could add up to 11% additional filtration efficiency. However, fabric and fabric combinations were more difficult to breathe through than N95 masks.

Conclusions: The current coronavirus pandemic has left many communities without access to N95 face masks. Our findings suggest that face masks made from layered common fabric can help filter ultrafine particles and provide some protection for the wearer when commercial face masks are unavailable.

Keywords: infection control; infectious diseases; public health; respiratory infections.

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Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1
Figure 1
Diagram of experimental apparatus using two P-Trak Ultrafine Particle 8525 counters for simultaneous measurement and a TSI 9565 VelociCalc to measure face velocity.
Figure 2
Figure 2
The filtration efficiency of tested fabrics and fabric combinations with error bars showing 95% confidence. Heat-n-Bond (HnB); Wonder Under (WU).
Figure 3
Figure 3
A comparison of existing data on fabric ultrafine filtration. Data chosen represent the highest velocity for each study. Data from this study were adjusted to proportionally represent a velocity of 0.2 m/s for this comparison. Data from Rengasamy et al are estimated from the included graphs, as statistical information about the data was not provided.
See this image and copyright information in PMC

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