Police are extending a trial of a new type of pepper spray more potent than the regular kind.
Officers have been trialling a liquid version of the spray in Bay of Plenty since November last year and will carry out a six-month trial of a gel-based spray in East Cape and Hawke's Bay.
Police say because the new spray contains six times more capsicum than normal pepper spray, it acts more quickly and takes longer to wear off.
They say the gel-based spray is also less affected by wind and has a longer range, though it's slightly more difficult to aim.
The Police Association says regular pepper spray sometimes doesn't incapacitate people quickly enough, so they have to resort to more risky tools like tasers or firearms.
But a senior criminology lecturer at Auckland University of Technology, John Buttle, says there has been little research done on the long-term effects of pepper spray and making it more potent increases the danger of breathing problems.
Inspector Jason Ross says police can manage any potential health risk as all officers are trained in first aid specific to pepper spray and carry first aid kits, including Ventolin to help people who may have respiratory problems.