Hospital workers and paramedics in Macarthur will join more than 22,000 medical staff planning to strike over fears about workplace safety.
NSW Health Services Union delegates voted on Tuesday to take industrial action in the fight to improve safety conditions on the job.
They are calling for at least 250 additional security staff in metro hospitals.
Workers will take industrial action for four hours on August 1.
Macquarie Fields-based paramedic Tess Oxley, assistant secretary of the south west Sydney Health Services Union sub-branch, said she wanted the public to know that no one's health would be affected by the industrial action.
"We really want the public to get behind us and understand why we're taking this action and know that we're not doing anything that's going to jeopardise anyone's health," she said.
"We feel that we've been left with no other alternative to get the government to give us the protection we need to do our jobs and ensure we take the best care of our patients."
Ms Oxley said paramedics could not strike, so their industrial action would be a little different.
"We will be wearing high-visibility uniforms and removing all billing information from our paperwork during the four-hour window," she said.
"This means we'll be doing our paperwork by hand instead of electronically and during that period no one we go out to will receive a bill from us."
Ms Oxley said she encountered instances where patients were unstable, threatening and harassing staff and other patients, causing many people to feel unsafe.
Campbelltown MP Greg Warren said he backed the Health Services Union members.
"I am fully supportive of the plight of these workers," he said.
"Ultimately it is important for the safety of our hospital staff and their ability to look after patients.
"I think the Health Services Union needs to be applauded for this."
State opposition health spokesman Ryan Park called on the government to sit down with health workers and address their "deep and justified concerns" regarding the safety of patietns, workers and members of the public at hospitals.
"Hospital staff are not punching bags," he said.
"They are right to be angry with this government. [Their safety] is crucial and the Liberals and Nationals are doing nothing to address the issue."
The industrial action will cover paramedics, allied health, catering, administration and security staff from across the state.
Nurses and midwives, however, will not be taking part.
The NSW Nurses and Midwives Association released a statement offering their HSU counterparts support.
"The rising level of violence and aggression being experienced by health workers is abhorrent," the statement said.
"This is a systemic issue across the entire health sector - public, private, aged care, mental health and community health workers are all being impacted.
"Nurses and midwives offer their in-principle support to the Health Services Union members who have voted to take protected industrial action.
"However, rostered nurses and midwives will remain at the bedside in hospital and other health settings across the state."
A NSW Health spokeswoman said the department would seek the assistance of the NSW Industrial Relations Commission to resolve any planned industrial action by the HSU.
The spokesman said there had also been an increase in security staff across NSW from 974 full time equivalent staff in 2010 to 1243 in 2018.
Data from workers compensation claims show injuries to staff from assaults has continued to decrease since 2016, the spokeswoman said.