Nurses at Victoria's Thomas Embling psychiatric hospital walked off the job for two hours on June 14 because of safety concerns.
The Health and Community Services Union said there had been 100 incidents at the hospital in the past three months, including one in which four people were injured.
Thomas Embling has 116 beds and most patients are transferred from the prison system or ordered by the courts to undergo psychiatric assessment or care. It has housed some of Victoria's most dangerous psychiatric patients, including Masa Vukotic’s killer Sean Price.