As firefighters with the California Department of Forestry and Fire Protection risk their lives battling wildfires in the state, they are joined by a group of nearly 4,000 inmates.

California has relied on its prison population to help fight fires since World War II. Today, inmates serving time for nonviolent crimes make up nearly 40 percent of firefighters, saving the state $100 million per year.

Some critics say the program is slave labor — inmates often receive no death benefits and make just $2 an hour — and even supporters are concerned about safety. But many inmates also say the work is fulfilling.

In an op-ed in The Washington Post, author Danielle Allen writes that was the case for her cousin Michael Allen, who has since died but was serving time for an attempted carjacking and was assigned to a fire camp in 2003. Michael wrote in his journal about how the work allowed him to challenge himself and be out in nature.

"Prison is obviously, partly by design, a very stark and deprived and monotonous environment, and so I completely understand how the opportunity to be out in nature is attractive to many prisoners, and the opportunity to do something constructive and to do something that serves and helps other people," says David Fathi, director of the ACLU's National Prison Project.

But while Fathi (@DavidCFathi) says jobs for prisoners can have a positive impact, prisoners also represent a "uniquely vulnerable part of the workforce."

"When prisoners do volunteer to work it's especially important that we make absolutely sure that they're making a free and uncoerced and truly voluntary choice," he says. "And that's especially important when the work they're doing is very dangerous, like fighting wildfires.

"At least two [inmate firefighters] have died in California. Six prisoner firefighters died in a single fire in Arizona back in the '90s. So this is not a theoretical concern. This is very dangerous work."

Interview Highlights

On prisoners' lack of worker protections

"Prison is a uniquely coercive environment, and there's very little in prison that's truly voluntary. And that's why it's so important that we make sure that these choices are insofar as possible, fully informed and truly voluntary. Right now, prisoners are a very vulnerable workforce: They can't unionize. They can't go down the road to take a different job if they don't like the one they've got. They're not protected by minimum wage and other laws. If they're injured or killed on the job, in most states they're not covered by workers' compensation.

"This is a situation where the usual checks on employer exploitation and abuse really don't apply. And we think the solution is that prisoner workers have to be protected by the same laws as all other workers so that you reduce ... that cost differential and that temptation to exploit prison labor, because it's cheap, because it's docile, because it's less empowered than other work."