With gold-standard N95 respirators in critically short supply at hospitals, underwear and T-shirt factories in the U.S. have retooled to make cotton face masks so doctors and nurses will have some protection.

Companies from New Balance and L.L. Bean in New England to Gap in California are contributing to an ever-widening emergency initiative, the likes of which hasn’t been seen for 80 years. The effort offers a lifeline for the garment industry, its sales flattened by the pandemic.

Several underwear and T-shirt factories are working with the White House to supply masks for hospitals. HanesBrands Inc., which is supplying many companies, made material in the Dominican Republic, transported it to Miami in military planes and trucked it to American Giant’s factory in Middlesex, North Carolina.

Clothing manufacturer SanMar Corp. last week began giving employees mask-sewing training in its Knoxville, Tennessee, factory.

“This is our Manhattan Project,” said Renton Leversedge, a SanMar executive. “People are coming with all sorts of ideas on how to improve them. Everyone from upholstery sewers to grandma in her basement want to help.”

The Federal Drug Administration and the U.S. Department of Health and Human Services helped configure the pattern used in the masks. The cotton masks aren’t recommended for use when treating coronavirus patients, but medical staffs are desperate.

Peter Navarro, President Donald Trump’s trade adviser, said the federal government will reimburse companies for their costs and distribute what they produce. HHS and the Federal Emergency Management Agency will buy the masks and distribute them to medical organizations immediately or use them to replenish the government's stockpile.

The goal is to swiftly ramp up production to 10 million masks a week, according to the National Council of Textile Organizations.

Garment factories are turning out three-ply jersey cotton.

It’s unclear how effective the masks will be in curbing the spread of the virus known as COVID-19, which can be transmitted through droplets when a person coughs. In some cases, doctors are wearing three-ply jersey masks over their N95 masks, so they can use the more heavy-duty ones longer.

Marcus Schabacker, chief executive officer of ECRI Institute, a non-profit organization that researches healthcare procedures and devices, said the cotton masks could help stem infection rates if distributed widely to confirmed or suspected virus patients. They won’t protect a doctor or nurse because of how close they must get to treat patients, he said.

“The masks are going to be helping, but it’s a band-aid, it’s not going to heal the wound,” Schabacker said.

The mask campaign got underway on March 18, when Navarro hosted a call with companies including Hanes. Parkdale Mills Inc., a North Carolina yarn maker, spearheaded the meeting, according to manufacturers.

The question was how, and how fast, factories could rejigger production lines and supply chains. American Giant dispatched an engineer and mechanic to get its factory ready and is acquiring extra folding and binding machinery, said Chief Executive Officer Bayard Winthrop. He estimated the company will start producing 35,000 masks weekly.

“We could scale to complete capacity at our plant and still not be making enough,” Winthrop said.

To keep employees safe, the factory is conducting temperature checks, creating more space between workers and stressing the importance of hand-washing.

AST Sportswear Inc. started turning out masks after hearing about shortages at local hospitals. Based in Brea, California, AST repurposed the 100% cotton fabric it has on hand. Chief Operating Officer Abdul Rashid said the company was motivated by news reports about healthcare workers “putting together makeshift masks out of little pieces of paper.”

The COVID-19 crisis has reminded many of World War II, when companies transformed themselves, shifting from consumer goods to war supplies. Since then, America's clothing labels have largely moved production abroad to take advantage of cheaper labor. Today, factories are counting on plants in Vietnam and China to churn out gear for U.S. medical personnel. Gap Inc., for instance, said it has shifted resources in its global supply chain so some suppliers can make gowns, scrubs and masks.

Some companies are getting in the act on their own, not as part of the White House initiative. In New York, Ralph Lauren Corp. has pledged to work with US factories to produce 250,000 masks and 25,000 isolation gowns.

In Maine, L.L. Bean is in contact with medical organizations to figure out how it can shift to medical-related production at its local factory, which usually makes duck boots and hunting shoes.

New Balance, which has five plants in Maine and Massachusetts, is working with the Massachusetts Institute of Technology and local hospitals to create face masks, test swabs and other medical equipment by using its 37 3D printers. CEO Joe Preston said he expects larger-scale production to start happening soon. His factories have been closed for the past two weeks but would reopen for this project.

“We're hearing what the shortages are: face masks, swabs and ventilators," Preston said.

An army of volunteers, including fashion designer Cynthia Rowley, is pitching in, too. Holed up in her New York studio, Rowley is making masks out of leftover bonded and neoprene fabrics from her label’s swimsuits. They’re not medical-grade but might at least help people from spreading germs, she said.

“Everything helps, and I need to do what I can,” said Rowley, who will donate what she sews.

Everyday citizens are also getting into the act, churning out masks on sewing machines. Such homemade fare are a “last resort,” according to the U.S Centers for Disease Control & Prevention. “Their capability to protect healthcare personnel is unknown” and “caution should be exercised when considering this option,” the agency said on its website.

JoAnn Fabrics Inc.’s stores are handing out material for free, and the company posted a mask-making video tutorial. Dallas resident Taylor Reed said JoAnn inspired her; with one yard, she can sew as many as eight masks. It takes her about 30 minutes to knock one out. “This is my way to contribute,” she said.