2.1 Selection of heaters
Six of the nine households tested were participants in a Warm Homes trial funded by the Ministry for the Environment. Households were selected on the basis that they had a suitable heater and were willing to participate. As part of the programme, the households chosen had a pre-1994 wood burner replaced with an NES-compliant wood burner. Three additional households willing to participate in the sampling programme were located with the assistance of the South Waikato District Council, and these already contained NES-compliant wood burners.
Fuel was not supplied for the study. Instead, each household burned whatever they would normally burn. The moisture content of a representative portion of the fuel was measured using an electronic moisture meter. Where moisture meter readings indicated a very high moisture content samples were returned to the laboratory and moisture content was determined by oven drying. Participants noted on a worksheet what fuel was burned on a particular day.
2.3 Emissions sampling
A portable emissions sampler was installed in each household for the duration of the tests. Results from the sampler can be used to calculate an emissions rate in g/kg (dry-wood basis) independently of any information recorded by the householder. The method employed by Applied Research Services is based on the Oregon Method 41 (OM41), also known as the Condar Method.
Filters on the samplers were changed daily, and where possible the sampler was run for seven days in each household. Further details on the sampler are given in Appendix 3.