Vacuum bags have stirred controversy as a material for homemade masks.

Controversy has erupted over whether it’s safe to construct a homemade mask out of a vacuum bag to fight the spread of the new coronavirus.

The Oregonian/OregonLive was among the media that reported earlier this week about a Cambridge University study that tested a range of commonly found household items as DIY mask material candidates -- including T-shirts, tea towels, scarves and linen.

The researchers found vacuum bags to be one of the top performers, filtering out 94 percent of airborne particles. Other studies looked at sweatshirts, pillowcases and cotton bandanas, but the vacuum bags outshined nearly all of them.

Our story included a link to a popular YouTube video by Dr. Ryan Southworth, an emergency medicine doctor in Arizona, who recommends a HEPA filter vacuum bag.

Some readers responded with questions about the safety of vacuum bags, and referenced London doctor Simon Freilich, who said in a YouTube video that making a mask from a HEPA vacuum bag is “a really, really awful thing to be doing.” He said the bags are made from “glass microfiber” that can damage the human respiratory system. Many Americans refer to those microfibers as fiberglass.

After some pushback from YouTube viewers saying the bags they’d checked didn’t have dangerous glass fibers in them, Freilich posted that he couldn’t research “every possible type” and that there “are clearly various types of filters and materials out on the market.”

That has, in turn, spurred a spate of testimonials from people in the vacuum bag industry.

One came from Josh Wolcott of Vacuums R Us near Denver, Colo., also on video. He denounced the idea that vacuum bags contain fiberglass as a myth. Wolcott said his research included contacting various manufacturers and looking over safety data sheets that describe bag materials. He found no vacuum bags that contain fiberglass, he said.

Another vacuum cleaner industry member, Vacuum Cleaner Market of Morgan Hill, Calif., also was adamant in its response. “Vacuum bags have not ever, and do not contain fiberglass,” read a statement on the company’s website.

But a prominent vacuum bag manufacturer, Shop-Vac, has issued a statement saying its products aren’t intended “to protect humans from bacteria, viruses or other pathogens," though it didn’t allude to what its bags are made of.

“Under no circumstances should anyone attempt to make a mask or mask material from any filters manufactured, sold or distributed in the market for or by Shop-Vac Corporation,” read the company statement.

The company couldn’t be reached to offer an explanation, including whether fiberglass is included in its vacuum bags.

Health experts agree that fiberglass particles are dangerous to inhale, and homemade masks shouldn’t be made from materials containing fiberglass.

To be sure, you might want to check with the manufacturer of any vacuum bag you’re thinking of using before making a mask.

Or try using some other highly rated materials in from the Cambridge University study. They include tea towels, which with two layers filtered out 96 percent of particles, or a T-shirt, which filtered out 69 percent.

-- Aimee Green; agreen@oregonian.com; @o_aimee

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