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1 • Thursday, May 14, 2020 - McHenry County News

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McHenry County News VOL. 10 • NO. 21

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THURSDAY, MAY 14, 2020

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Making a homemade COVID-19 mask? Study explains best fabric choices

By Lois Yoksoulian, Physical Sciences Editor UNIVERSITY OF ILLINOIS, COLLEGE OF ACES

Health authorities believe COVID-19 spreads by the transmission of respiratory droplets, and the Centers for Disease Control and Prevention recommends homemade cloth face coverings for use in public spaces. Illinois joins many other states in requiring people to wear masks while out. However, initial uncertainty regarding the masks’ effectiveness in reducing exhaled droplets leaves some people unsure or skeptical of their usefulness during the current COVID-19 pandemic. Mechanical science and engineering professor Taher Saif spoke with News Bureau physical sciences editor Lois Yoksoulian about a study that he and his graduate students, Onur Aydin and Bashar Emon, performed on the effectiveness of common household fabrics for use in homemade masks. Physically speaking, are the respiratory droplets produced by talking and breathing the same as those that come from a cough or a sneeze? The droplets released during sneezing and coughing are larger than those released while speaking and breathing, and any of these droplets may carry many virus particles. The larger droplets tend to fall nearby due to gravity, but the smaller ones can go far, with the majority of them remaining within six feet of the infected individual. Unfortunately, because symptomatic, pre-symptomatic and asymptomatic carriers can shed the coronavirus, we cannot tell without testing which individuals are the sources of infection. Hence, a physical barrier, such as a mask, can prevent the spreading. How does droplet type influence the fabric choice and the number of layers used to make a mask? The droplets released during coughing and sneezing come in various sizes and velocities. The fabric for any mask should be breathable and impermeable to high- and low-velocity droplets. It is important to realize that a highly impermeable fabric is likely to be less breathable. Low breathability will force airflow through the sides and will defeat the purpose of the mask. In that case, the mask simply gives a false sense of safety. The choice of fabric and the number of layers is a matter of compromise between breathability and droplet resistance. We need to maximize both. What fabric properties did you test? We tested the breathability and droplet blocking ability of common household fabrics. To quantify breathability, we simply measure the airflow velocity through the material. Measuring droplet blocking is a more complicated process that uses an inhaler to generate high-velocity droplets. We fill the nozzle of an inhaler with distilled water mixed with 100-nanometer fluorescent particles, which mimic the coronavirus in size. When puffed, the inhaler forces the water through the nozzle and generates high-momentum droplets that we

TAHER SAIF PHOTO McHenry County News

Mechanical science and engineering professor Taher Saif, right, and students Onur Aydin, left, and Bashar Emon test common household fabrics used to make facemasks to help stop the spread of the coronavirus.

collect on a plastic dish placed vertically in front of the inhaler. We then repeat the process with the fabric we are testing over the collection dish. We measure how much water landed on the dish in both cases by counting the nanoparticles using a microscope. We can then use the ratio of the volume collected with and without the fabric to give us a measure of droplet-blocking efficiency. What types of fabric did you examine? We considered a set of 10 common household fabrics and com-

pared their properties with those of a medical/dental-quality mask as a benchmark. The fabrics had different combinations of cotton, polyester and silk. We also measured the breathability and resistance for twoand three-layered T-shirt fabric. Our work produced two key findings. First, most common household fabrics, such as T-shirt material, have 40% or higher droplet blocking when used as a single layer. In two layers, to our surprise, T-shirt fabric had a 98 percent droplet blocking efficiency–exceeding that of the

medical mask, while maintaining better breathability. Second, most common fabrics are hydrophilic, meaning they up soak water, whereas medical masks are hydrophobic, meaning they repel water. This tells us that common household fabrics use an alternative mechanism to hold droplets by retaining them. What type of fabric do you recommend for the home mask maker? We found that very breathable fabrics are a good choice, like com-

mon T-shirt materials. They tend to have low droplet resistance, and their efficiency increases when used in a two-layer mask. The net breathability of the two layers is much higher than the medical masks, too. In fact, the breathability of cotton T-shirt fabrics remains higher than a medical mask, even with three layers. Homemade masks can be an effective tool for the public, together with testing and contact tracing, social distancing and other interventions to mitigate disease transmission.

ComEd taking steps to support customers Company suspending service disconnects, providing resources and payment accommodations

In coordination with work being led by Illinois Gov. J.B. Pritzker, Chicago Mayor Lori Lightfoot, and Cook County Board President Toni Preckwinkle to protect Illinoisans, ComEd is taking action to help its customers with payment assistance programs and by imposing a moratorium on service disconnections and waiving new late payment charges through at least May 1, as many businesses and institutions are following guidance from the Centers for Disease Control and Prevention by taking temporary measures to shut down or limit operations to control the spread of COVID-19. ComEd is also taking steps to expand awareness of the programs in place to help customers through temporary or extended financial hardship and will be working with customers on a case-by-case basis to establish payment arrangements and identify energy

assistance options. “We know this time is difficult for so many of our customers, who may be experiencing health or economic challenges, and we want to be there to help them navigate the support available to them,” said ComEd CEO Joe Dominguez. “Through our own programs, as well as those offered by community and government partners, we’re committed to working with every customer who contacts us.” “As one of the largest nonprofit community action agencies in the country, we see firsthand the impact that the necessary business slowdowns to slow the spread of this virus has on the people we serve,” said Harold Rice, president and CEO of the Community and Economic Development Association of Cook County, Inc. (CEDA). “We appreciate the support and partnership of ComEd in stepping in to help people who may now be

facing an even greater hardship.” Payment Options Customers who struggle to cover their energy expenses have a growing range of assistance options from ComEd. The company offers financial assistance programs and flexible payment options, all of which can help eligible customers reduce budget strain and avoid disconnection of service. Particularly during this time when some customers are facing unforeseen circumstances, ComEd will work on a case-by-case basis with customers who are struggling to pay their energy bills to help them remain in service. ComEd offers payment options such as budget billing, which averages payments out over a 12-month period to help customers manage their monthly energy bill, and flexible

See COMED, Page 2


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