Researchers from Baltensperger's laboratory have found that the amount of secondary aerosols that are released from a wood-burning stove can vary dramatically depending on the design of the stove and the type of wood fuel used.

Using a high-resolution time-of-flight aerosol mass spectrometer, PhD student Maarten Heringa and his colleagues analysed the emissions from two different log wood-burners and a residential pellet-burner under different combustion conditions. "To our surprise, we saw a tremendous increase in total organic mass within a few hours," Baltensperger told environmentalresearchweb. "We used xenon arc lamps to simulate sunlight and found a dramatic increase in organic matter as soon as we switched the lights on."

Secondary organic aerosols are formed when organic gases emitted by wood-burning stoves are oxidized in the presence of sunlight to give organic particulate matter. The two log wood-burner experiments showed a substantial increase in organic matter for both starting- and flaming-phase emissions but no secondary organic aerosol formation was observed for the stable burning phase of the pellet burner. This is believed to be because of the very stable and controlled burning conditions for the pellet burner in contrast to the log-wood ovens. The researchers also found that a modern wood-burning stove produced fewer aerosols than an old wood-burning stove.

"This shows that the choice of how the wood is burnt is important," said Baltensperger. "Emissions from wood burning can have a major impact on air quality and therefore on human health. It is important that we find ways of burning wood so that it does not release these aerosols."

Now Baltensperger and his colleagues plan to use their experimental technique to analyse emissions of chimneys. They also plan to work with manufacturers of wood-burning stoves, filters and catalytic converters to improve the efficiencies of the products.

The researchers have published a discussion paper in the journal Atmospheric Chemical Physics.