Homemade facemasks: particle filtration, breathability, fit, and other performance characteristics

Abstract

Homemade cloth masks and other improvised face coverings have become widespread during the COVID-19 pandemic driven by severe shortages of personal protective equipment. In this study, various alternative (mostly common household) materials, which have not traditionally been used in respiratory protective devices, were tested for particle filtration performance and breathability. Most of these materials were found of some—but rather limited—utility in facemasks. At a breathing flow rate of 30 L min⁻¹, 17 out of 19 tested materials demonstrated collection efficiency below 50%; at 85 L min⁻¹, only one material featured particle collection efficiency above 50%. Pressure drop values were mostly below 4 mm w.g. (observed in 89% of cases for the two flow rates), which provides comfortable breathing. Only for one fabric material (silk) tested at 85 L min⁻¹ did the pressure drop reach 11 mm w.g. Based on these results, a three-layer facemask prototype was designed and fabricated comprised of the best performing materials. Additional tests were conducted to examine possible particle detachment/shedding from the materials used in the newly developed facemask, but no such phenomenon was observed. The prototype was evaluated on 10 human subjects using the standard OSHA-approved quantitative fit testing protocol. The mask protection level, determined as an adopted fit factor, was found to lie between that of the two commercial surgical/medical masks tested for comparison. A 10-cycle washing of the mask prototype lowered its collection efficiency across the particle size range; however, washing did not substantially affect mask breathability. The study revealed that although homemade masks offer a certain level of protection to a wearer, one should not expect them to provide the same respiratory protection as high-end commercial surgical/medical masks or—by any means—NIOSH-certified N95 filtering facepieces.

Keywords:

• Cloth mask
• COVID-19
• face covering
• fit
• particle collection efficiency

Acknowledgment

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Disclaimer

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Additional information

Funding

Funding for this study was awarded by the University of Cincinnati College of Medicine and Office of Sponsored Programs under the Special Coronavirus (COVID-19) Research Project Grant Program. Partial support was provided by the National Institute for Occupational Safety and Health through the University of Cincinnati Education and Research Center (Grant T42OH008432).