A human rights lawyer is concerned prison guards with full access to pepper spray will result in more violence.
Currently prison guards have to get approval from prison directors before using pepper spray.
Human rights lawyer Michael Bott says guards could be more likely to reach for the spray rather than trying to "diffuse" a situation first.
"If you've got those forms of increasing force, then often reliance on persuasion and talking and engagement with the person takes second place."
The rule change comes in next month, and is being introduced to help guards handle potentially dangerous situations including when escorting prisoners in cars.
It's crucial staff are immediately able to control spontaneous situations to keep both themselves and prisoners safe, Corrections Minister Louise Upston said on Wednesday.
"Pepper spray is a safe tactical option with a lower risk of injury compared with other means of force," she said.
Pepper spray adds to other safety equipment that has been rolled out to Corrections staff in recent years, including stab-proof vests and body cameras.
It's the same spray used by police, and guides for carrying and using the spray will be redeveloped.
NZN / Newshub.