NSW public hospital workers including paramedics, allied health and security staff plan to strike for four hours as they fight for increased hospital security.

Public hospitals across NSW could descend into chaos with more than 22,000 workers planning to strike over fears about workplace safety.

More than 500 NSW Health Services Union delegates on Tuesday voted unanimously to stop work for four hours on August 1, as they fight for increased security at the state's hospitals.

HSU NSW secretary Gerard Hayes warned August's strike is just the start of the union's planned action until the state government addresses and fixes the security "crisis" in hospitals.

"This won't be the end of it," Mr Hayes told reporters in Sydney.

"We've seen too many people stabbed, too many people shot, too many people who have been spat upon or punched."

The union has called for at least 250 additional security staff in metro hospitals.

Mr Hayes said having appropriately resourced security staff will enable them to proactively intervene rather than react to issues as they happen.

Security, allied health, catering and administration staff, as well as paramedics, will take part in the action across the state but Mr Hayes has assured patients won't be put at risk.

Paramedics will continue to respond to emergencies but won't go forward with "more routine matters", he added.

HSU member Tess Oxley said paramedics recently had to move a patient from a hospital's emergency department back into the ambulance because it became unsafe for all of them.

"There were other patients from the hospital that were unstable, that were threatening, that were harassing and patients and families were raising concerns that they did not feel safe," she told reporters alongside Mr Hayes.

NSW Labor health spokesman Ryan Park called on the Berejiklian government to provide additional staff and to improve training so workers can better deal with difficult and drug-affected patients.

"Hospital staff are not punching bags. The safety of health workers, patients and members of the public is crucial and the Liberals and Nationals are doing nothing to address the issue," he said in a statement on Tuesday.

A NSW Health spokeswoman said the department will seek the assistance of the NSW Industrial Relations Commission to resolve any planned industrial action by the HSU.

There has been an increase in security staff from 974 full-time equivalent staff in 2010 to 1243 in 2018, the spokeswoman said.

Peter Anderson has been appointed to review security in NSW hospitals and his final report is due later this year.

Data from workers compensation claims show injuries to staff from assaults has continued to decrease since 2016, the spokeswoman said.

About $19 million has been invested on security capital works in NSW emergency departments and over $5 million to upgrade personal duress alarms for staff to make EDs safer, the spokeswoman said.

The NSW Nurses and Midwives' Association said nurses and midwives offer their in-principle support to the HSU members who voted to take industrial action.

"However, rostered nurses and midwives will remain at the bedside in hospitals and other health settings across the state," a statement from the NSWNMA said on Tuesday evening.

"Current violence prevention measures are clearly inadequate and require urgent attention."