Concerns over safety and security saw more than 500 Health Services Union members from hospitals throughout the Illawarra Shoalhaven Local Health District take part in a statewide stoppage on Thursday.

Across the state more than 22,000 health workers - including security, allied health, cleaning and administrative staff - took part in the industrial action.

At rallies outside both Wollongong and Shellharbour hospital just after 10am, members voted to maintain the action over four hours - while members at some NSW hospitals scaled back the action to one hour.

HSU organiser for Wollongong Hospital Mark Jay said it was time for the NSW Government to invest in hospital security.

"We're not asking for a pay rise, we're asking to be able to come to work each day and feel safe - and it's not happening," he said.

"There's not enough staff to deal with the ongoing security issues - I've worked in health for 17 years and things have become dramatically worse over that time.

"Our emergency departments are turning into war zones due to rapid population increases and the changing landscape, which includes a rise in ice addiction.

"Health workers are being injured on a daily basis, and those who are out on workers' compensation are not being replaced, making matters worse."

Mr Jay said as well as additional staff, there was an urgent need for better education and training - and better protections for staff whose job it was to protect others.

"We need legislation to protect our workers - so security guards are able to restrain and detain people in an effective manner without the fear of being prosecuted themselves."

Outside Shellharbour Hospital, members chanted 'Stand up, fight back' as motorists beeped their horns in a show of support.

HSU Shellharbour branch president Michael Twyford said assaults on staff were increasing at the hospital - which houses the majority of the region's mental health units.

"It's only a matter of time before someone is seriously injured or killed," he said.

"If there's an incident in one of the mental health units, and security are dealing with an issue in the ED - there's no plan B, as there's just not enough staff."

Skeleton crews of support staff were in place at hospitals across the region, and the state, during the industrial action to ensure patient care was not compromised. But there were delays.

Nurses and doctors remained at work, though their unions supported the HSU action.

HSU members voted to strike on July 16, and the union has been negotiating with the NSW Ministry of Health in the NSW Industrial Relations Commission over the past week.

On Wednesday afternoon HSU NSW secretary Gerard Hayes confirmed the strike would go ahead after negotiations failed to resolve the union's concerns about the security crisis.

Mr Hayes said while the ministry had agreed to a trial of new security measures at one of the state's local health districts, it needed to take more than "baby steps" to solve the issues.

However a NSW Health spokesperson said the government remained "committed to addressing security issues with its workforce and ensuring that our hospitals are safe and welcoming places for our staff, patients and visitors".

"The NSW Government appointed Peter Anderson to review security in NSW hospitals and to look for any improvements that can be made to practices to ensure staff, patients and visitors are further protected," the spokesperson said.

"In February 2019, Mr Anderson released an Interim Report and action on those recommendations is already underway.

"Mr Anderson is continuing his review, visiting hospitals in rural and regional areas, to understand the security challenges that exist in those facilities.

"Mr Anderson has spoken to hundreds of front line staff as part of his review. A final report will follow in the final quarter of 2019."

The spokesperson said that across NSW, $19 million had been invested to improve security in emergency departments at public hospitals.

This included upgrading CCTV systems, improving access controls between public and staff areas and installing remote locking to public access doors.

In addition, more than $5 million had been invested to upgrade duress alarms for staff in emergency departments, which they are mandated to wear while on duty.

Meantime Mr Hayes said Thursday's strike was the beginning of a campaign that will only intensify.

"The level of violence against hospital workers is sickening. There are more than 40 assaults in NSW hospitals each month," he said.

"In the last three years, our members have been shot, stabbed, punch, bitten and spat upon. Enough is enough.

"We are extremely proud of our members who walked off the job. These members have sacrificed pay to stand up both for their own safety and also that of the general community."