A state-run unit for troubled teenagers has been criticised for locking up youngsters for up to 12 hours each night.
The health watchdog found the outcome for some children living in Crannog Nua in north Co Dublin was poor due to their complex needs not being met and inadequate management of risk-taking behaviour.
The Health Information and Quality Authority (Hiqa) also raised concerns over the welfare and safety of youngsters and about the number of runaways from the high support unit (HSU) - with 134 unauthorised absences in the past 12 months.
"The continuous risk-taking behaviours of children that included fire setting, substance misuse when absent from the unit, and behaviours that included bullying and physical threats toward other children and staff, reflected the complex needs of the children, but also demonstrated that the systems in place to protect children and keep them safe were not effective," it found.
Four teenagers were living in the unit when it was visited by inspectors unannounced last October. The open residential service is for children in care who require specialised support and is not a detention centre.
The authority said practices such as the routine locking of doors impinges on the children's rights and detains children in a way that is not within the legal remit of the HSU.
It said some practices used to respond to risk-taking behaviour, such as locking units from 8pm to 8am, had also become institutionalised.
"The inspectors were unable to establish the legal remit for restricting children's freedom of movement," it added.
Hiqa warned fire assessments did take into account the fact that all external doors were locked overnight, nor did it consider the increased risk of fire due to the profile and behaviours of the children.
While it commended several areas of care, it found children were placing themselves at risk of harm by absconding. One teenager revealed sanctions imposed after were minimal and did not change their behaviour.
Records also showed there were also a significant number of reports related to bullying incidents between children.
"These included verbal threats and physical assaults," Hiqa said.
"Records reviewed by inspectors showed that individual and group work was carried out directly with children in relation to bullying and that these incidents were appropriately reported to relevant parties."
Despite measures to tackle the issue, and staff intervening, some children told inspectors they did not feel safe all of the time, it added.
Elsewhere it found the Health Service Executive's Children and Family Service did not have sufficient special care beds available, meaning staff were dealing with children with high-risk behaviours.
"Such children were not suitably placed in an open residential setting at this time," it added.
"Although the HSU made every effort to meet children's needs safely it was not always possible or sustainable to do this."
Gordon Jeyes, chief executive of the new Child and Family Agency, said inspections are an integral part of the child care system and said more beds were becoming available for youngsters in care.
"My main priority is that where the agency takes on the care of a young person in a unit such as Crannog Nua, it ensures the care, protection and education of that young person, as any good parent would," he added.