Preliminary Evaluation of the Filtration Efficiency of Alternative Mask Filter Materials
DOI:
https://doi.org/10.26209/psjm61989Keywords:
COVID-19, Personal Protective Equipment, surgical mask, filter material, medical maskAbstract
Purpose: The purpose of this project was to evaluate the filtration efficiency of selected household materials and commercial fabrics for use in mask construction to provide protection from the SARS-CoV-2 virus (COVID-19).
Methods: A particle counter was utilized to measure particle penetration through each of the material samples and filtration efficiencies were calculated for the following particle sizes: 0.3 µm, 0.5 µm, 1 µm, 3 µm, 5 µm, 10 µm. Samples included a N95 respirator, KN95 respirator, cleanroom mask, MERV 13 and 15 HVAC filters, paper towels, polypropylene shop towels, meltblown fabric, surgical sterilization wrap, cotton, and various wools. Some samples were measured in multiple layers.
Results: The N95 respirator, meltblown fabric samples that were layered in 4 or more plys, and 2-ply MERV 15 bag filter had a filtration efficiency consistent with the NIOSH requirements for an N95 respirator with filtration efficiencies at 0.3 µm of 98.0%, 95.4%, and 95.1%, respectively. Of the samples tested that did not meet the N95 specifications, the cleanroom mask and KN95 respirator were the closest, with a filtration efficiency at 0.3 µm of 86.3% and 83.9%, respectively. Of the non-traditional filter materials tested, the sterilization wrap layered in 2 or more plys, paper towels in 3 or more plys, and some of the wool felt samples had filtration efficiencies that were markedly superior to those of the cotton and shop towel samples.
Conclusions: While some of the filter materials tested had a filtration efficiency that met NIOSH N95 respirator requirements, most of the non-traditional filter materials tested were inferior to commercially manufactured masks. However, when used in multiple plys, some did provide superior filtration to the materials currently recommended to the public for mask use. Therefore, they may be beneficial for use in homemade masks for the public or as a layer in a composite mask for healthcare workers. Further testing of these materials for filter parameters such as pressure drop, durability, and safety is recommended before using them to produce masks.
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