Household Materials Selection for Homemade Cloth Face Coverings and Their Filtration Efficiency Enhancement with Triboelectric Charging

Abstract

The COVID-19 pandemic is currently causing a severe disruption and shortage in the global supply chain of necessary personal protective equipment (e.g., N95 respirators). The U.S. CDC has recommended use of household cloth by the general public to make cloth face coverings as a method of source control. We evaluated the filtration properties of natural and synthetic materials using a modified procedure for N95 respirator approval. Common fabrics of cotton, polyester, nylon, and silk had filtration efficiency of 5–25%, polypropylene spunbond had filtration efficiency 6–10%, and paper-based products had filtration efficiency of 10–20%. An advantage of polypropylene spunbond is that it can be simply triboelectrically charged to enhance the filtration efficiency (from 6 to >10%) without any increase in pressure (stable overnight and in humid environments). Using the filtration quality factor, fabric microstructure, and charging ability, we are able to provide an assessment of suggested fabric materials for homemade facial coverings.

Integrating IAQ control strategies to reduce the risk of asymptomatic SARS CoV-2 infections in classrooms and open plan offices

“…To reduce the number of virus-containing aerosols emitted to the space from any possible virus carriers present, universal face masking (as well as hand sanitizing before entering the space) is essential. It can reduce the average emission rate by about 95%, 75% and 50% (i.e., by a factor of 20, 4, and 2) with N95, surgical and cloth masks, respectively when properly worn (Chen and Willeke 1992, Zhao et al 2020, and Mueller et al 2020. Wearing a mask also significantly weakens the exhaled air jet and reduce the mixing and spread of virus contained in the exhaled air.…”

“…Standalone room air cleaners with HEPA filters can also be used as a supplementary measure to further reduce the concentration of virus in the occupied space. Zhao et al (2020) reported a range of clean air delivery rate (CADR) from 170 to 800 m 3 /h (or 100 to 470 CFM) with a median cost of $361 and a median electrical consumption of 56 W per unit based on a comprehensive survey of off-the-shelf air cleaners available from the most popular websites for shopping. The results were consistent with an earlier laboratory study in which 6 portable air cleaners were tested for both particulate and volatile organic compounds removal performance (Chen, Gao, and Zhang 2006).…”

Face Masks Against COVID-19: An Evidence Review

“…There was over 90% penetration for all cotton masks and handkerchiefs, and 50%-60% penetration for surgical masks and non-woven non-medical masks. Zhao et al used a similar approach, but at a lower 32L/min (which is still 3-6 times higher than human ventilation during light work) (92). They also tested materials after creating a triboelectric effect by rubbing the material with a latex glove for thirty seconds, finding that polyester achieved a quality factor (Q) of 40 kP/a, nearly ten times higher than a surgical mask.…”

A novel reusable anti-COVID-19 transparent face respirator with optimized airflow

“…Due to the lack of face masks, many global health authorities recommended wearing homemade ones or those provided by any supplier. Generally, these are made by one cloth layer to prevent an infected person from transmitting their viruses to others by respiratory droplets [14]. Nevertheless, it has very low efficacy in drastically limiting the transport of viruses to the nose or mouth of the wearer.…”