Rooms designed to safeguard children undergoing intensive care in hospitals will help combat their risk of catching infectious diseases that could worsen their conditions.

The NSW-first isolation rooms will be built into the cancer care wards and intensive care units at both The Children's Hospital at Westmead and the Sydney Children's Hospital in Randwick.

Children aged four and under have the highest rates of hospital emergency department presentation Australia-wide of any age cohort besides people aged 85 and over.

Deputy Premier Prue Car said walking through the Westmead pediatric centre to visit a prototype facility was a sobering moment.

"As parents, we never want to have to be in the situation where we need a children's hospital," she said on Wednesday.

The Children's Hospital at Westmead prototype has been developed to allow staff the chance to familiarise themselves with the room's layout and technology before the official roll-out begins for admitted patients.

The isolation rooms are expected to be completed at both Sydney children's hospitals in 2025.

Known as Positive Pressure Ventilation Anterooms, the facilities use a ventilation system that prevents air coming in from outside the room and stabilises infection control.

The rooms will function as a protective shield to help reduce the risk of young, immune-compromised patients being exposed to viruses and other potential infections while in hospital.

Health Minister Ryan Park said new facilities were "absolutely critical" and would help patients and families who were navigating often-complex health issues.

"These children are not here for a night or two," he said.

"Sometimes they're here for weeks and months on end, and it's very, very important that we provide them with world-class health care."

Premier Chris Minns said the facilities would save lives by ensuring seriously ill children could safely stay in hospitals for long periods.

"(They will) ensure that we get more kids who go through these complicated procedures can be rehabilitated in public hospitals and then get on with the rest of their lives," he said.

Carer zones are also being introduced at the two sites for parents and carers to remain in hospital with children while they are in intensive care.