NEW YORK (NYTIMES) - Inside the rural Ohio labs run by Battelle, a non-profit research and development firm, scientists have tested explosives, experimented with atomic energy and worked with chemical nerve agents. But some of the group's most critical work is now happening outside, in a carpark.

Under a sprawling tent near the small town of West Jefferson, employees have spent recent weeks decontaminating more than 30,000 used face masks for doctors and nurses on the front lines of the coronavirus pandemic.

Each day, N95 masks collected from more than 100 hospitals, clinics, fire departments and nursing homes are treated for hours with a hydrogen peroxide vapour. Once cleaned, the masks are sent back to the same facilities to be reused.

A severe shortage of personal protective equipment has left hospitals desperate as the outbreak continues to spread.

Automakers, fashion designers, furniture manufacturers, tech companies and other organisations have in recent weeks been rushing to manufacture and distribute new masks - part of a growing and improvised effort to increase the supply.

For Battelle, which usually develops products across a range of disciplines, from robotics to oil drilling, the decontamination project is an attempt to extend the lives of masks that already exist.

Late last month, Battelle was granted emergency authorisation by the Food and Drug Administration to expand its decontamination efforts, following pressure from President Donald Trump and Ohio Governor Mike DeWine.

Battelle said its process, what they call the Critical Care Decontamination System, will eventually be able to clean 80,000 masks a day per site and that each mask can be cleaned up to 20 times before losing effectiveness.

Hundreds of employees are involved, and thousands more are being hired, with many going through training to set up decontamination sites in New York; Seattle; Boston; Washington, DC, and elsewhere.

For now, the bulk of the operations are happening roughly 30km west of downtown Columbus.

Like many efforts under way, Battelle's project was barely an idea three weeks ago. The company had used vaporised hydrogen peroxide to sterilise sensitive equipment for years. But to develop a large-scale decontamination process, the logistics were hurriedly sketched out on a conference room table by a handful of experts and executives.

Battelle's West Jefferson site has since received scores of face coverings, double-bagged and stored in boxes marked with biohazard symbols. Healthcare networks like OhioHealth and Mercy Health are delivering their used masks by courier. Recently, the chief of a local fire department dropped off masks in person.

Up to 50 boxes, containing thousands of masks, show up every day. The number of boxes is expected "to grow exponentially" as hospitals work out safe collection procedures, said Mr Kevin Sayers, who is helping to oversee the West Jefferson operation.

In early April, Mr DeWine said that Battelle would decontaminate masks for free for two weeks.

Preparing newly arrived masks for decontamination requires small teams of workers in the tents, each wearing black rubber boots, two layers of gloves, surgical scrubs, a lab coat and a portable, powered air-purifying respirator attached to a belt that blows filtered air into a closed hood over the worker's head.

Each mask is inspected before it is processed; roughly 10 per cent are soiled or broken and cannot be decontaminated, according to Mr Sayers.

"We're seeing a lot of masks right now that have make-up on them," he said.

When ready to be decontaminated, the masks are brought inside a 1,000-cubic-foot chamber.

Inside the decontamination chamber, the teams position the masks, in batches of 5,000 per cycle, on wire shelves affixed to the chamber's metal walls, taking care to avoid overlapping.

The workers then exit the chamber, spraying themselves with a 70 per cent alcohol solution. The precaution requires a gallon of alcohol each day.

A contraption known as a vapour phase hydrogen peroxide generator, which looks like a washing machine with two hoses, is then used to circulate the colourless gas into and out of the room. During the first four hours, workers increase the humidity inside the chamber, causing the hydrogen peroxide to collect as condensation on the masks, neutralising the coronavirus and other contaminants.

Over the next four hours, the gas is flushed out of the room. The teams then re-enter the chamber to inspect the masks and conduct spot tests for harmful levels of residual hydrogen peroxide. They then confirm that chemical indicator cards placed throughout the chamber have changed colour - the sign of a successful decontamination.

Before being repackaged and sent back to hospitals, the masks are individually marked with the number of decontamination cycles they have passed through.

Last week, for the first time since the effort began, a mask was submitted for a repeat cleaning.

"It was nice to see a mask come back," Mr Sayers said. "It means that it has been used multiple times and will continue to be used instead of being thrown out."

As more sites start decontaminating masks and more hospitals participate, Mr Sayers expects Battelle to start accepting deliveries all day and through the night. The organisation hopes to win approval to expand its procedure to other types of personal protective equipment, such as face shields and surgical masks.

One aspect of the effort, however, worries Mr Sayers: the number of people needed to run decontamination shifts as the pandemic continues to overwhelm the medical community.

"It requires a team of dedicated people working a lot of hours," he said. "We're going to need more and more manpower as the need continues to grow."