Particle pollution from wood burning can be assessed by either measuring particle mass or particle number. Particle mass is still the usual way how emissions and air quality concentrations are officially measured in the course of type approval or with monitoring stations. However, 80 to 90 percent of particles from stoves and boilers are less than one micrometer in size – a large share is even ultrafine (below 0.1 micrometer) and thus very harmful. That is why measurements of Clean Heat focused on particle number.
Clean Heat conducted more than 50 measurements in Germany, Denmark and other EU Member States. These measurements provided us with important information regarding the level of particle pollution caused by wood burning and enabled comparisons with other emission sources:
- Indoor measurements: Due to the use of a firewood stove, indoor concentrations of ultrafine particles can increase substantially (from 2,000 to more than 100,000 particles per cm3). Results of the indoor measurements are depicted in our case study 'Pollution from residential burning' and in our scientific poster.
- Outdoor measurements (ambient air): Residential areas in which a lot of wood burning occurs experience similar or even higher pollution levels than the most highly polluted roads. Outdoor measurements are good indicator for the environmental impact of wood burning appliances. However, they are not valid for legal purposes, for example in the case of neighborhood disputes. Results of the outdoor measurements are depicted in our case study 'Pollution from residential burning' and in our scientific poster.
- Emission measurements (in or at the chimney): The number of particles emitted by a stove or boiler can be reduced by at least 80% by using an effective precipitator or filter. Results of these measurements are depicted in the reader of the conference "Staubmessverfahren an Kleinfeuerungsanlagen" (presentation by Axel Friedrich) and were presented at the press conference with the Berlin ice-cream maker Florida Eis.