Surveillance officers are going out in Christchurch's suburbs at night monitoring the use of non-compliant log-burners in a bid to reduce the city's smog.
Canterbury Regional Council estimates 10,000 of the city's 130,000 households have woodburners more than 15 years old.
Spokesperson Katherine Trought said two officers had been going out for four nights each week for the past few weeks and using thermal imaging technology to look at chimneys.
Ms Trought said of the 100 houses surveyed, 29 inspection notices had been issued, with the residents being asked to give explanations.
But Labour Party MP for Christchurch East Poto Williams said the council could be doing more to consult locals and bring them on board, and that many people did not have a choice about how they kept warm.
"Our housing costs have gone up markedly in the last few years, and there may be people who are renting homes who actually are finding the increase in housing costs, plus the increase in power costs, just a little too difficult."
The council aims to have no more than three high pollution nights per year by 2016; 12 have been recorded already this year.
