Beware of neighbours offering you free firewood or traders selling building offcuts on Trade Me.
Building offcuts are always treated timber which is illegal to burn (for good reason).
"A Government-funded study released recently by the Ministry for the Environment confirms that air pollution from home heating, transport and industry causes almost 1,000 premature deaths in New Zealand each year and costs around $1.1 billion a year."
http://www.gw.govt.nz/story23209.cfm
I have mentioned this practice to TM and hopefully this will be brought to a halt.
If you notice anyone burning treated timber, you can report them to your local Regional Council (they will have a Freephone number) . Link to Regional Councils.