The effects of operating conditions on emissions from masonry heaters and sauna stoves

Emissions from masonry heaters and sauna stoves were studied. In the sauna stove the production of organic gaseous carbon (OGC) at 10 gC kg⁻¹ (per kilogram of fuel), carbon monoxide (CO) at 55 g kg⁻¹, fine particle mass (PM₁) at 5 g kg⁻¹ and number emissions (N) at 1.8 × 10¹⁵ kg⁻¹ was higher than in other measured appliances. In a modern technology masonry heater with a unique grate, the emissions were very low: 0.4 gC kg⁻¹ OGC, 14 g kg⁻¹ CO and 0.7 g kg⁻¹ PM₁. Conventional masonry heaters, using small logs, clearly produced higher emissions when compared to using large logs. Doubling the fuel load caused emission factors to increase by up to 4- times (OGC), except for the number emission, which decreased from 4.0 × 10¹⁴ to 2.0 × 10¹⁴ kg⁻¹. From the conventional masonry heater 90% of the PM was emitted during the firing phase. Its combustion process is different to that in stoves or conventional open fireplaces. The insufficient supply of air, due to too fast pyrolysis, and increased ash release, due to the high combustion temperature, are the main parameters which cause high particle and gas emissions in masonry heaters and sauna stoves.