E-cigarettes are an increasingly common sight in rural county jails, according to The New York Times. Sheriffs are selling the devices to inmates to help control mood swings, and to increase revenue.

Most prisons and jails ban traditional cigarettes, because of fire hazards and secondhand smoke, the article notes. Jails selling e-cigarettes can use the revenue to pay their guards more. In many jails, guards earn little more than fast-food workers. In some communities, revenues from e-cigarette sales to prisoners go into the county’s general fund.

Federal prisons ban e-cigarettes. In county jails in at least seven states, a limited selection of flavors of e-cigarettes are sold to inmates. Chinese and American e-cigarette manufacturers are now making “jail-safe” versions, which are made from plastic instead of metal. E-cigarettes are sold to prisoners for $8 to $30 each, depending on how many puffs they provide.

In Macon County, Tennessee, Sheriff Mark Gammons says at least half of the jail’s 150 inmates smoke, and many use e-cigarettes. The jail purchases each e-cigarette for $2.75, and sells it for $10. Gammons hopes to collect between $20,000 and $50,000 from e-cigarette sales this year.

County sheriffs say since they have introduced e-cigarettes, there has been a decrease in violence and tension in jails. “When these guys get in here they’re wound up anyway, and then you tell them they’re not getting cigarettes, and it’s on,” said Jason Armstrong, who runs inmate accounts at the Greene County Detention Center in eastern Tennessee, which began selling e-cigarettes in September. “Now, they’re pretty much getting their nicotine fix, so it’s cut down on altercations.”

E-cigarette distributors are encouraging the trend, lobbying local officials and leaving samples at jails. The website of Precision Vapor, based in Lexington, Kentucky, states, “Earn thousands of dollars for your jails while curtailing nicotine withdrawal of your inmates.”