Environment Southland air and terrestrial science team leader Dr Nick Talbot said in a statement winter was when Southland experienced its poorest air quality, particularly in the urban areas of Invercargill and Gore.
"Home heating is one area where people can make the biggest difference to our air quality," he said.
"Not only does burning wet wood create a large amount of smoke, it gives off much less warmth than dry wood."
Dr Talbot attributed the sharp decline in exceedances in 2019 and since 2021 to people changing the way they used their burners.
"The decrease of PM10 exceedances in the Invercargill airshed in 2019 and since 2021 is due to several factors, one of those being the change in burning behaviour, with people using more dry wood and less banking of fireplaces, resulting in the overall emissions of air pollutants dropping."
He also believed phasing out older burners alongside cleaner forms of home heating being installed contributed to the decrease.
Air Quality Collective director Ian Longley said weather also affected the readings.
"Air quality emission trends are always difficult to see ... because air quality is also very sensitive to changes in the weather. Two thousand and nineteen was a good year for air quality weather-wise (windier and/or not as cold) and 2020 was a bad year (calmer/colder)."
But where the readings had shown an increase in the latter data, he suspected some of the initial changes had not been sustained over the longer period.
Environment Southland’s winter air quality monitoring season runs from May 1 to August 31.
The regional air plan includes rules to help improve air quality in the Invercargill and Gore airsheds. Open fires are now prohibited and non-compliant burners are being progressively phased out.
For those outside the airsheds, consented fireplaces of any kind may still be used, as long as they are not used with prohibited fuels such as rubbish and treated wood.
Outdoor burning is prohibited within the Invercargill and Gore airsheds. Those outside the airsheds can continue to burn but must adhere to a number of rules, including not burning prohibited items such as baleage wrap and treated timber.
"During the damp, shorter days of winter, outdoor fires tend to produce more smoke, which can be a nuisance to your neighbours. Elevated smoke levels increase the risk of hazardous particulates accumulating, leading to potential health impacts and the possibility of exceeding air quality standards," Dr Talbot said.
Environment Southland operates a Good Wood-approved suppliers’ scheme, in which firewood retailers voluntarily agree to supply wood at the recommended moisture level of less than 25%.
- Toni McDonald
