Inmates are breathing easy following the prison smoking ban with scientists finding a greater than 50 per cent rise in air quality and – to everyone's surprise – no major incidents since the big stub out.

Smoking was banned in New Zealand prisons on June 1 last year with stark warnings from prisoners, prison advocates, and guards of riots and disorder.

However, there were no riots and Corrections staff report a number of unforeseen benefits.

Prison services assistant general manager Rachel Leota said prisons had reported a "calmer" environment with fewer "standover" incidents now that tobacco has been taken out of circulation.

Inmates had been heard on the prison telephone monitoring system telling family they appreciated living in a smoke-free environment and encouraging family to give up.

Prisoners had more money to spend on things such as phone cards, she said.

A team of scientists from Auckland University studying the amount of "fine particulate" in the air of prisons has found the rate halved after smoking was banned.

Dr Simon Thornley and colleagues set up an air quality monitor in Auckland Prison, at Paremoremo, and measured fine particulate concentrations for 15 days before and 15 days after the ban.

Readings were already low as the detector had to be set up in a staff area for safety concerns.

Before the ban the mean concentration was 6.58 micrograms per cubic metre of air.

This dropped to 5.17mcg once a ban on sale of cigarettes was introduced and fell further to 2.44mcg once the total ban was implemented. Thornley said despite the dramatic increase in air quality, the thing that surprised people the most was how well-behaved prisoners were while the ban was introduced.

"There were all sorts of preparations – extra staff, having riot gear available," he said.

Thornley credited the department for the long preparation time they had invested in the ban, communicating to inmates and helping them give up cigarettes.

"This is the most comprehensive prison ban we've seen [worldwide]," he said.

Because there was no possibility of having a cigarette, people seemed to be more able to accept it – similar to how even heavy smokers are able to handle long-distance flights without a cigarette.

"It seems the comprehensive ban is the most effective," he said.

"My sense is, a lot [of inmates] smoked because they were bored, and they could." Leota said there had not been a significant rise in contraband smuggling.

There were still a few incidents of prisoners trying to smoke their nicotine replacement patches though this was mainly new prisoners and those on remand.