The Otago Regional Council (ORC) is reminding landowners that having an outdoor fire permit for an autumn burnoff does not allow them to burn indiscriminately and without regard for the environment.
The council is investigating several recent complaints where smoke from outdoor bonfires on the Taieri Plain caused air pollution.
ORC environmental services manager Martin King said the fires were lit this week when there were low inversion conditions, so the smoke was hitting the inversion layer and then drifting, hanging low over the land, and spreading out over wide areas across the Taieri.
"It's a situation where it's all very well having a fire permit, but that does not mean people can burn whenever they like," Mr King said.
"People need to read the permit and check the ORC rules for the discharge to air, which primarily means not causing objectionable and offensive smoke beyond a property boundary."
Landowners needed to factor in prevailing wind conditions when deciding whether to light an outdoor fire, Mr King said.
"People thinking of burning autumn prunings must be aware that when there are still conditions, it's likely to be accompanied by a low inversion layer. The smoke will be trapped under the inversion and may well cause a nuisance to neighbours."
ORC staff spent half a day earlier this week investigating a complaint of excessive smoke and then saw numerous other potential breaches, which were also investigated.
Mr King said if emissions were found to be offensive and objectionable under the Otago Air Plan, landowners may be subject to enforcement action.
The council is investigating seven possible breaches and repeat offenders could be prosecuted.
"With reasonably heavy atmospheric conditions and a low inversion layer you don't get dispersion, all you get is smoke which lingers," Mr King said.
He urged people to think of other ways to deal with autumn prunings and other garden material, such as composting or shredding. ORC defines outdoor burning as:
burning in the ground
on the ground
in a container
outside a building
in a heap
in a drum or incinerator
burning of standing vegetation
The ORC operates a pollution hotline on 0800 800 033 which people can use to report nuisance fires.