The head of Colorado's Department of Corrections announced he's ending the use of long-term solitary confinement as punishments for inmates in the state.

Executive Director Rick Raemisch made the announcement in an opinion piece the New York Times published online Thursday.

It’s not a complete end to solitary confinement, but it does mean that inmates will not be secluded for longer than 15 days. Previously, some prisoners would spend years in isolation with limited contact to anyone else.

Restrictive housing, administrative segregation, the SHU, the hole and lockdown are all terms for solitary confinement in prison.

The National Institute of Justice, under the U.S. Department of Justice, studied the common prison practice and in a 2016 book called the isolation technique, "among the most extreme measures (short of deadly force) available to prison and jail officials."

"I feel it was a bad tool to begin with so it's something that has become so misused that it's time to take it out of the tool box," Raemisch said.

In Colorado, that's what the DOC executive director did in September and told the country about it in the New York Times op-ed this week.

Solitary is a severe consequence to breaking prison rules. Raemisch believes keeping someone in forced solitude for more than 15 days is torture, which is why that is the new limit in Colorado.

"In a sense, mental torture. I believe it to be very harmful to the mental capabilities of individuals," Raemisch said.

According to a study by the Bureau of Justice Statistics, the use of restrictive housing was linked to inmate mental health problems.

In his opinion piece, Raemisch said Colorado has "developed alternatives" to solitary confinement for prisoners.

"If they're involved in a serious assault against one of our staff members or another inmate, once the criminal charges are over they're going to be moved out of state," he said.

However, once inmates are transferred out of state, they could end up in solitary if that prison system deems the isolating punishment is warranted.

Raemisch said currently there are 18 inmates in solitary confinement, spending at most 15 days there. In the op-ed, he explains for those prisoners in isolation, they could also get therapy or take anger management classes.