What makes for a good homemade face mask?
What makes for an effective homemade mask?
Everybody and their brother is doing experiments on all sorts of household goods, including T-shirts, furnace filters, winter scarves, paper shoptowels, coffee filters and more.
The U.S. Centers for Disease Control and Prevention's instructions for making homemade masks call for using “cotton fabric” or a T-shirt.
It does not specify what kind of cotton fabric: Broadcloth? Gauze? Flannel? Jersey? Terry cloth? Muslin?
Cotton was chosen because it is breathable and easy to wash, a CDC spokesman said Tuesday.
The CDC's instructions call for making a multi-layer mask, sandwiching a paper coffee filter between the fabric layers.
A professor at Missouri Science and Technology University, Yang Wang, has gained some attention after he tweeted results from a quick experiment he and a doctoral student did on several masks they made. Wang is an assistant professor of environmental engineering, specializing in aerosols.
They tested a scarf, furnace filters, a bandana, 400-thread-count pillowcases and 600-thread-count pillowcases. The high-count pillowcase did best among the fabric options, followed by the scarf (fabric and weave unspecified), the 400-count pillowcase, then the bandana. Each was used to make a four-layer mask.
Some people are concerned that using cotton will make them sick, because cotton holds moisture longer than some other fabrics and so could keep incoming coronavirus-containing particles from drying out.
A 2011 randomized controlled study of about 1,600 health care workers in Vietnam compared doctors and nurses who wore medical-grade masks (not N95 respirators) to those wearing cloth masks, when treating patients with symptoms of influenza. Medical-grade masks did a better job than the cloth masks at blocking particles. Particles got through medical masks 44% of the time but through cloth masks 97% of the time, according to the study.
It also noted that workers wearing the cloth masks were given instructions to launder the masks themselves with soapy water, but the researchers did not monitor compliance.
“Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally,” the researchers from the University of New South Wales wrote. “However, as a precautionary measure, cloth masks should not be recommended for (health care workers), particularly in high-risk situations, and guidelines need to be updated,”
They urged more study, saying little work had been done on the topic, because in poorer countries, many health care workers do not have access to N95 respirators and medical-grade masks.
Some social media advice includes using furnace filters in masks, but the manufacturer of Filtrete filters advises against it.
“Our filters are designed to be used in HVAC systems, and the filter media has not been tested to be used as a face mask for respiratory protection. Altering any of our 3M Filtrete Air Filters is not recommended or supported by 3M or the Filtrete Brand. Customer safety is our number one priority,” a statement says.