The Ministry for the Environment has set a National Environmental Standard (NES) of 50 micrograms of PM10 per cubic metre of air (averaged over 24 hours). The Canterbury airsheds of Christchurch, Timaru, Ashburton and Kaiapoi must reach three exceedences per year by 1 September 2016 and one exceedance allowed by 1 September 2020. The airsheds of Rangiora, Geraldine and Waimate must reach one exceedance per year by 1 September 2016.
PM10 is particulate matter in the air that's 10 microns in diameter or less. You can't see something that's PM10-sized without using a microscope. A microgram is a millionth of a gram.
50 micrograms of PM10 per cubic metre of air doesn't sound like a big deal, but in fact PM10 at that concentration is associated with significant respiratory health problems for people.
Other pollutants from home heating are carbon monoxide (CO) and sulphur dioxide (SO2). The Ministry for the Environment has also set National Environmental Standards (NES) for CO and SO2.
Carbon monoxide from home fires exceeds the NES occasionally, but sulphur dioxide from home heating does not usually exceed the NES.
In all Canterbury's "air sheds" (an air shed is all the the air above a particular place: there is an air shed for Christchurch, and another for Timaru, Ashburton, Rangiora, and so on) burning wood and coal for home heating causes most of the PM10 pollution. Some pollution is also caused by transport and industry. The amount emitted from these sources is estimated in emissions inventories.
On calm days in winter, home heating with wood and coal can cause air pollution to build up, especially in the evening when the wind often dies down on clear nights.
Although most of the pollution happens in winter, you may still see what looks like a pollution haze at other times of the year. As PM10 pollution is measured year-round, our monitoring checks whether the concentrations during such days do not breach the NES. In the summer the haze is more likely to be caused by natural particles such as dust, sea salt and moisture.
The weather does not cause pollution but can influence whether pollution accumulates near its source.
On still, cold winter nights a temperature inversion can occur: when the ground is cool, the air closer to the ground can be colder than air higher up. Cold air is denser than warm air and does not rise, so cold air will stay close to the ground. This means that smoke from home chimneys will not rise or blow away, but will get trapped - causing high levels of pollution.
Temperature inversions are typically formed when there is little or no wind and the sky is clear.
If there is wind, pollution will generally be blown away and diluted and pollution levels don’t generally reach high levels. The weather forecast is therefore an important factor in forecasting air pollution.
Environment Canterbury has rules for woodburners and open fires in Chapter 3 (Air Quality) of the Canterbury Natural Resources Regional Plan. The rules are different depending on your situation and where in Canterbury you live. Environment Canterbury is also working with District Councils to develop clean heat programmes that are specific to each town.
Open fires are the most polluting and inefficient form of heating - up to 85 % of the heat generated by an open fire goes right up the chimney and is not used to heat your home. Older solid fuel burners are also more polluting and less efficient than modern, low-emission burners. If you use an open fire or older solid fuel burner to heat your home, consider replacing it with a less polluting heating system such as a flued gas or diesel fire, electric heat pump or an approved low-emission woodburner or pellet fire.
Insulation will keep the heat in, meaning you will need to generate less heat, causing less pollution. Many homes have substandard insulation, where only a thin layer was installed or the insulation has deteriorated. Ideally a layer of approximately 200 mm should be installed (R3.5).
Subsidies are available through the Government's Warm Up New Zealand: Heat Smart programme to install insulation and clean heating appliances. Check out www.energywise.govt.nz to see if you are eligible.
If you would like to report any pollution, please call the pollution hotline on 03 366 4663 (Christchurch), 03 688 3320 (Timaru) or 0800 765588. The pollution hotline operates 24 hours a day, 7 days a week.
(03) 353 9007
0800 324 636 (EC INFO)
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