Union E tu believes attacks on security guards are happening all too often.
In the latest attack, a prisoner assaulted a Corrections officer using sharp plastic at Christchurch Men's Prison.
The officer drew his pepper spray "bravely and quickly" during the attack, prison director Jo Harrex told Newshub, and the prisoner "became compliant".
"The officer has received treatment at a local medical centre and been taken home, and will be provided with ongoing support."
E tu's Sam Jones says it needs to stop.
"From our perspective, it's fairly frequent. One assault that leaves a worker maimed at work is not good enough. It happening on a regular basis is absolutely unacceptable."
In a similar incident, a Waikato Hospital security guard was attacked and suffered severe injuries and faces a long recovery.
Jones says it's just the tip of the iceberg - he knows of "at least six cases where security guards have suffered serious assaults in our hospitals", many afraid they'll lose their jobs if they speak out.
"We know of guards who have left the industry and profession because of assaults, and because of not feeling safe on the job."
WorkSafe is being urged to step in, Jones saying guards are often understaffed and poorly trained by "budget" security firms.
"We think that WorkSafe need to reassess their recent categorisation of security as not being high-risk. THere was a death in the last six months - not the first death in New Zealand."