Development of a compact technique to measure benzo(a)pyrene emissions from residential wood combustion, and subsequent testing in six modern wood boilers

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are emitted during incomplete combustion of organic materials and are particularly harmful to human health. As a representative of PAHs, Benzo(a)pyrene (BaP) is restricted by the European Union to an annual average value of 1 ng m−3 in ambient air. This threshold is significantly exceeded during the heating season in various regions. Residential wood combustion furnaces are considered to be a major source for BaP pollution.In this research, a compact sampling method for BaP measurements was validated. Afterwards, the method was used to assess emissions from modern automatic wood boilers, in order to obtain a detailed knowledge of BaP emissions from residential wood combustion furnaces.It was demonstrated that, for a wide range of BaP concentrations, sampling from the hot flue gas of residential wood combustors can be carried out effectively over a simple quartz filter, after proper dilution with cold purified air. Highest BaP emissions from the investigated boilers occurred during start, with a mean concentration value of 6.3 μg m-3. All values refer to standard conditions (273.15 °C, 100 kPa) and to an O2 volume fraction of 13% in the dry flue gas. The lowest concentrations occurred during full load operation (mean value 73 ng m-3 at STP). It was found that, amongst all flue gas compounds analysed, elemental carbon is the parameter most closely related to BaP. This work demonstrates, at optimal operating conditions, modern automatic wood boilers have potentially lowest BaP emission concentrations amongst residential wood combustion furnaces.