Aerosol emissions from logwood combustion increase significantly when the emission ages in ambient air. A significant increase occurs already within three hours of aging, according to a new study from the University of Eastern Finland. The emission increase was caused by the formation of secondary organic aerosols (SOA) in which gaseous organic compounds, released during the combustion, oxidise and condense on aerosol particles. This observation is very important, because current emission inventories do not take SOA emissions into consideration at all.