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Woodburner emissions Updated: 25 Feb 2010

What's the problem?

Woodburner testing

For woodburner-compliance testing, the woodburner sits on accurate scales in a special test room where the heat output can be measured. Each test run is started with an existing hot ember bed. Cut lengths of clear (no knots) 100mm round, very dry radiata are used.

The scales allow a measured amount of fuel to be burnt down to a set residual weight. The flue is connected to several measuring instruments, and the average heat output, emissions, and efficiency are calculated from the measurements taken during the test run.

In order to achieve good results in this test, manufacturers design and "tune" their woodburners to burn as cleanly and efficiently using the same kind of fuel.

The trouble is, this test fuel is nothing like real firewood. Real firewood has more resin and other volatile compounds, and these require more air than the test fuel to burn. That means a woodburner tuned for the test fuel won't burn real firewood as effectively, with the result that more of the wood goes up the chimney in the form of smoke and soot.

And smoke and soot aren't good for you. Some of the microscopically-small particles they contain can lodge in your lungs, causing problems such as asthma and other respiratory diseases. There is no known lower "safe" limit for the pollution that woodburners produce.