A review is underway in New South Wales into the use of force and isolation in juvenile detention, after it emerged some detainees have been locked in their rooms for extended periods.

Key points: Under NSW legislation, detainees can be locked in their rooms for up to 24 hours

Under NSW legislation, detainees can be locked in their rooms for up to 24 hours Confinement and separation are necessary to manage high-risk detainees, centre manager says

Confinement and separation are necessary to manage high-risk detainees, centre manager says Experts say the rates of reoffending are high among juveniles

In one case, under the highly controversial but now defunct Chisholm Behaviour Program, a detainee was held in his room for 166 days out of 300.

But for many detainees at the Cobham Juvenile Justice Centre in Sydney's west, another concern is the rate of recidivism.

"Vincent" was just 11 years old when he committed his first serious offence and ended up in juvenile detention, and has been in and out ever since.

"Some people say I'm institutionalised," he said.

"I don't mind it in here, cause I come back and you see the same people around me.

"But on the outside I was raised up in DoCS, so I'd rather be in here than in DoCS."

Because Vincent was 11 when he first entered custody, he was locked in his room for his own protection for two weeks.

"It's a shit go, but there's nothing they can do, they can't mix me with other people."

"I was a bit of a smartarse back then."

'I was stressing out'

"Jay", 16, has also been locked in his room — but for punishment, not protection.

He said once he was "confined" for 12 hours.

In one case, a detainee was held in his room for 166 days out of 300. ( ABC News: Lindy Kerin )

"I was stressing out. I didn't like it in there, because I was just thinking about stuff, you know," he said.

Under NSW legislation, detainees can be locked in their rooms for up to 24 hours, and the department says 73 per cent of cases last for six hours or less.

Detainees can, however, be confined, separated or segregated for longer periods for safety or security reasons.

An independent review is investigating the use of confinement in the state, after it emerged some juveniles had been locked in their rooms for lengthy periods.

'There are occasions where you have to use force'

Last year, the centre's manager Michael Vita conducted a review of the Don Dale Detention Centre. ( ABC News: Lindy Kerin )

The Cobham Juvenile Justice Centre is the main remand centre for NSW.

It takes in offenders across the full spectrum from minor infringements to murder, manslaughter and terror related charges.

The centre's manager, Michael Vita, has worked in adult jails, immigration detention and has been working in juvenile detention for 17 years.

He said measures used at the centre were within reason.

"If you're posing an active risk and it's assessed that the risk is high, you'll then be managed in accordance with a regime which takes that into consideration.

"For example, three weeks ago three detainees set upon a 56-year-old youth worker, in effect taking her hostage.

"Obviously you have to manage that, those detainees were placed on a regime, where until we assessed their risk lessened, they were going to spend time in their room.

"Whether they're terror related or whether they're high-risk charges or gang affiliations, bikies, I manage them so they don't get to talk to each other."

Mr Vita said confinement and separation were some methods to manage high-risk detainees.

"On a day-to-day basis, when you're dealing with 75 kids, there are occasions where you have to use force," he said.

"From time to time they do try to assault each other and we have to intervene".

High level of recidivism among juveniles

Last year, Mr Vita conducted a review of the Don Dale Detention Centre after a series of incidents including the tear gassing of a group of teenagers.

He is expecting to be called to give evidence.

The Cobham Juvenile Justice Centre is the main remand centre for NSW. ( ABC News: Lindy Kerin )

"There is no comparison between the NSW juvenile justice system and what was the NT juvenile detention centre of 2014.

"All of our rooms are air conditioned, clean running water, toilets, en suites, televisions — we don't have spit masks, spit hoods, chairs.

"Our behaviour management plans are proven, and a lot of other jurisdictions ask for our expert advice."

But the rates of reoffending are high among juveniles.

"There is, unfortunately, a large group of recidivists," said Mr Vita.

"It's not unusual to release someone on a Friday or Thursday and have them back to following Wednesday or Thursday.

"It's unfortunate there is a revolving door, but there are success stories as well."

"Jay" (L) was once locked in his room for punishment for 12 hours. ( ABC News: Lindy Kerin )

Jay has landed back in custody about five times after reconnecting with his old friends and getting into trouble.

He started smoking drugs and drinking when he was 10 and said a lot of his offending was drug related.

In the 12 months he has been in custody this time, he has been seeing drug and alcohol counsellors and he has been going to school, where he has learnt to read.

"I'm doing my Year 11 in here now, so I want to finish school when I get out and that and try and get a job.

"When I get out of here, I'll try and not come back in here any more."

Vincent still has some time to serve and he is not sure what he will do when he gets out.

"I'm looking at two years. I'll be 20 at the time, so I don't really know," he said.

The NSW Government recently announced a $1 million package to help manage high-risk detainees in juvenile detention.

It said the youth detention population was at a record low, with around 260 children in custody.

The independent review into the use of force and confinement in juvenile detention is expected to finish early next year.