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Particle and gaseous emissions of a top-feed pellet stove were studied in laboratory conditions. Pellets made of separate stem and bark materials of five different wood species and a commercial pellet product were used as fuels. The study included the determination of the particle number concentration, size distribution, fineparticle mass (PM1.0), CO, CO 2 , NO x , and volatile organic compounds (VOC). The PM1.0 emission was analyzed for inorganic substances, organic carbon, and elemental carbon. Thermodynamic equilibrium calculations were performed to interpret the results from chemical analysis and to estimate the chemical composition of the PM1.0 mass emitted with various fuels. The bark fuels produced higher PM, VOC, and CO emissions than stem fuels. This was evidently related to the higher ash content of the bark fuels and was found to increase both the fly ash emission and the products of incomplete combustion. The fuel ash content correlated linearly with the PM1.0 emission. Among stem fuels, willow and alder produced higher PM1.0 emissions than birch, pine, spruce, and the commercial fuel. An exceptionally low PM1.0 emission was measured from pine bark combustion, which can be explained by the low ash content of the fuel. The main components in the PM1.0 were K 2 SO 4 , KCl, K 2 CO 3 , KOH, and organic material. Except birch fuels, around 60-80 mass % of potassium species were K 2 SO 4 based on the equilibrium calculations. In the case of birch fuels, because of the high chlorine content and low S/Cl ratios, around half of the potassium was KCl.

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Equipment consisting of annular denuders, a filter, and a polyurethane foam adsorbent was used for sampling 15 PAHs from the diluted emission from a heat-storing masonry heater. The denuder method was compared to the ISO 11338 method which was used for the sampling from hot and undiluted exhaust gas. The denuder method used with the exhaust dilution gave a realistic gas-particle distribution of PAHs in more atmospheric-like conditions compared to the sampling from undiluted exhaust gas where PAHs were almost totally in the gas phase. The results gained with the denuder method from the diluted exhaust are more relevant, e.g., from exposure and atmospheric processes point of view. The emissions from smoldering combustion conditions (SC) were compared with the emissions from normal combustion conditions (NC). The emission of each PAH was 7 to 14 times higher from SC than from NC, and the gas-particle distribution was shifted towards the particle phase due to increased condensation of PAHs. The PAHs could be divided into three groups based on their phase distributions. In the first group, PAHs existed mostly in the gas phase in both combustion cases; the vapor pressures of PAHs were lower than the saturation vapor pressures. In the second group, the gas phase was saturated and the concentration was almost the same in both combustion cases, whereas the particle phase concentration was higher in SC. In the third group, PAHs were