During her latest shift at work, Erin* was tear gassed, threatened with having her throat slit and had two badly beaten teenagers collapse in her arms.

Key points: Last Sunday detainees staged a 21-hour riot at the Frank Baxter Juvenile Centre near Gosford

Last Sunday detainees staged a 21-hour riot at the Frank Baxter Juvenile Centre near Gosford One guard told the ABC detainees "didn't even look human" as they engaged in frightening violence

One guard told the ABC detainees "didn't even look human" as they engaged in frightening violence An urgent review into the incident has been ordered by the NSW Government

As a guard at the Frank Baxter Juvenile Justice Centre on the NSW central coast, Erin said she did not know whether she would finish her horror 14-hour shift alive last Sunday.

Detainees at the centre staged a 21-hour riot in which they stole chainsaws and garden tools, armed themselves with metal poles and refused to come off the centre's roof.

Erin said she knew the situation had escalated beyond anything she had seen in her 13 years at the centre when the guards had to lock themselves in an office.

"The detainees were smashing the doors and windows as hard as they could with chainsaws and whipper snippers," she said.

"I wouldn't be here anymore if they got in."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 18 seconds 1 m 18 s Riot police attempt to control detainees atop the roof of the detention centre.

She said the boys responsible for the violence, who ranged in age from 11 to 16, did "not even look like humans" as they carried out their brutal attack.

"I'm quite surprised at the level of violence they had towards me when I've worked with them for such a long time and pretty much had good relationships.

"They would kill you if they could."

But detainee uprisings have become more common at the facility in the past two years Erin said, and in June workers even walked off the job and after an officer was assaulted.

Detainees jumping on the roof has now become a weekly occurrence and guards, who are not even provided with capsicum spray, feel powerless when violence erupts.

Erin* said she had stayed in the job because she found satisfaction in supporting some detainees. ( ABC News: Meghna Bali )

Authorities say Sunday's riot targeted sexual offenders within the complex and seven teenagers sustained serious injuries such as stab wounds and broken limbs.

"I knew when I saw eight to 10 boys go into a room at a time … I didn't know whether anybody was going to come out of that room," she said.

The boys also spread petrol on the ground, stole knives from the kitchen, wrestled guards and caused major destruction to the facility.

"How they did not set the place on fire I don't know … how there weren't deaths I don't know."

Erin said she had not been able to sleep, eat or leave the house since the riot, and although she wanted to return to work and make a difference to the boy's lives, she was scared.

She said no-one in management had been in touch with her and she had not received any counselling.

Centre a 'finishing school for jail'

John*, who also works as a guard at Frank Baxter, said he was always in a state of fear when he turned up to work and it was the detainees who were in charge.

"There's no discipline in the system anymore," he said.

"The boys know there's no consequences to bad behaviour.

"The department are not prepared to maintain the safety and security of the staff … they didn't listen, they've got no ears."

John* said management is failing staff, the detainees and all taxpayers. ( ABC News: Meghna Bali )

John described the centre as a "finishing school for jail" and said a large percentage of children returned after release.

Another guard who did not want to be named said they had been "screaming out for change".

"If the detainees wanted to kill staff they could have easily killed many. This is the scale of [what] could have happened. Without exaggeration."

The Minister for Families, Communities and Disability Services, Gareth Ward, said all staff had been offered support, with counselling available on and off site.

"Damage to the centre is still being assessed [and] a number of units remain closed for assessment and repairs," a spokesperson said.

Mr Ward has asked for an urgent independent review of the incident, which will be conducted by former police assistant commissioner Lee Shearer.

"Any detainees involved in instigating the incident will feel the full force of the law," he said.