For $2 a day or $1 an hour, scores of men and women are fighting the wildfires ravaging California’s wine country.

They’re on call 7 days a week, on the frontlines, and make up 35 to 40 percent of Cal Fire, the state’s firefighting force.

And they’re inmates serving time for nonviolent crimes. In recent years, some residents have called them “angels in orange.”

“It’s a real good experience. It’s better than sitting (in the prison) yard. I like getting in there and helping people,” one 33-year-old inmate, Deshan Heard, told the OC Register this week. Heard, of Los Angeles, is serving six years behind bars for robbery.

Heard is assigned to one of 43 conservation camps across the state, a network of prison-funded fire companies from the borders of Oregon to Mexico. The convict crew, run by the California Department of Correction and Rehabilitation and in part by Cal Fire or the Los Angeles Fire Department, has roughly 3,800 to 4,000 inmates a week.

About 200 of those inmates are women, battling a rash of infernos that are the deadliest California has ever seen. The fires have claimed the lives of 31 people as of Thursday night and left at least 400 people missing.

On Monday, a day after the blazes started, Gov. Jerry Brown declared a state of emergency for swaths of Northern California’s wine country, including Napa and Sonoma counties. The fires wiped out entire neighborhoods in Santa Rosa, decimating about 2,834 homes and 400,000 square feet of commercial space.

Given this devastation, “We need every firefighter we can get, whether it’s an inmate or not,” said corrections spokesman Bill Sessa.

One firefighter, Sandra Welsh, told NBC News recently, “We are the ones that do the line. We are the ones that carry the hose out. We’re the line of defense.” Welsh’s Malibu camp was on standby as firefighters battle a brush fire in Anaheim Hills. Women make up three of the program’s conservation camps, Sessa said.

As of Friday morning, about 235 jailbirds turned firefighters were assigned to Canyon Fire 2 in Anaheim Hills, Sessa said. Meanwhile, roughly 300 were assigned to hot spots in Sonoma, Solano, and Napa counties.

“Today alone we have 1,700 inmates (or about 16 crews) on a fire line somewhere,” Sessa said, adding, “We are not only fighting fires, but we also have to provide backup fire protection in parts of the state that are not burning.”

During these massive fires, it’s common for inmate crews to work 24 straight hours, followed by a day of rest. The inmates, wearing orange jumpsuits, put in the same hours as their civilian brethren in yellow suits. (The professionals make a minimum of $17.70 an hour, according to one AFP report.)

As Santa Rosa fires raged, some crews worked 72 hours before they got 24 hours of rest, Sessa said. Like civilians, the inmates work in rough terrain, carrying hand tools and 60 pounds of gear on their backs.

“We tell all the guys we pick: We will treat you like a firefighter. We will only treat you like an inmate if you make us do it,” Sessa told The Daily Beast. “That happens very rarely. Most inmates in these camps have earned the right to be chosen based on rehabilitation work while they are serving their sentence in regular prison.”

The program, which started in the 1940s, is constantly replenishing its ranks because the inmates complete their sentences or are paroled. Sessa stresses that placement in the fire crews is voluntary.

But last month, a candidate for lieutenant governor called the program “slave labor” and “abuse” on her website.

“No matter how you may want to dress it up, if you have people working for nothing or almost nothing, you’ve got slave labor, and it is not acceptable,” wrote Gayle McLaughlin, a former mayor of Richmond, California.

In response to such criticism, Sessa told The Daily Beast that people make “slave labor” claims because they’re looking from the outside in.

“On occasion you have a fringe candidate for elective office who thinks it’s a great sound byte to stick in a headline, but if you look at it from the inmate’s perspective, it’s difficult to call them enslaved when they’re volunteering to do the job,” Sessa said.

“Every inmate working in a fire camp raised their hand and volunteered to do it,” he added.

Sessa said the $1-an-hour for fire prevention is the highest paying job for a California inmate and has rehabilitative value. Some inmates, he said, have never even held a job before joining the firefighting program.

When the inmates aren’t on call, they earn $2 a day while at the camp.

“If they’re raising their hand and volunteering to do it and getting $76,000 a year in benefits before they ever go to camp, then this whole argument about enslavement makes no sense,” Sessa said, referring to what he said was the prison system’s annual cost to house an inmate.

Sessa estimated the state of California is saving taxpayers $90 million to $100 million a year through the program.

“These inmates are not necessarily confined to fighting fires where they camp,” Sessa said. “Quite often they move hundreds of miles in a day, depending on where they’re needed.”

“All of these inmates can be moved in a moment,” he said, adding that crews from San Diego are working in Sonoma. “They move constantly.”

The firefighters work in crews of 14 people. They live in supervised fire camps when they’re not in the field. When they’re not on a fire, they usually work on fire prevention or conservation projects, such as cutting brush or taking out a grove of diseased trees.

While TV footage shows civilian firefighters in airplanes or water trucks, the inmates have a different role: They cut fire breaks by hand—or clear stretches of land—to stop the spread of flames, Sessa said.

“When you hear on the news that a fire is X percent contained, that is in some part from what our crews do,” Sessa said.

The inmates use hand tools, with a lead firefighter using a chainsaw to cut trees and others using axes and shovels. “Every person in line has a job related to the person behind them in line,” Sessa added.

Still, the work is not without danger. This year, two inmates died in the line of fire.

Matthew Beck, 26, died in May when a 120-foot tree uprooted and crushed him in Humboldt County, about 300 miles north of San Francisco. Beck was serving six years for a 2014 burglary in Los Angeles County.

In July, Frank Anaya was killed in San Diego after he slashed his leg with a chainsaw. The 22-year-old died after undergoing several surgeries. Anaya, of Ventura County, was serving a three-year sentence for spousal assault and weapons offenses.

Anaya’s fatal injury marked the fifth death in the program’s 40-year history. “When you consider the decades this has been in place, the safety record has been outstanding,” Sessa said when asked about those who lost their lives.

A debate has long swirled around the program.

As The Daily Beast previously reported, the California attorney general’s office argued against an early prison-release program in 2014 because they believed it would “severely impact fire camp participation.”

In response, David Fathi, director of the ACLU’s National Prison Project, said such dangerous work outside of prison walls had a risk of government abuse. The inmate firefighters may also not be aware of the long-term health risks, he said.

Yet in the press, the prisoners themselves are praising their roles.

“This is the first time in a long time my family is proud of me,” Travis Reeder, a 23-year-old imprisoned for drug dealing, recently told AFP.

In 2015, one firefighting convict said he volunteered for the program because the conservation camp gave him freedom.

Then-34-year-old Joshua Coover told the East Bay Times that working all night to clear hazardous vegetation was “the best feeling in the world.”

“The best feeling is when we get off the fire; all the signs you see that say ‘thank you, firefighters,'” Coover told the Times. “They even refer to us as the ‘angels in orange.'”