The black carbon of the air (BC) refers to strongly light-absorbing particles which contain a substantial amount of inorganic carbon. Black carbon is formed by incomplete combustion. In the Helsinki Metropolitan Area, the emission sources include diesel vehicles, wood burning, ship traffic and long range transport. Black carbon belongs to the size category of fine particles (PM2.5).
HSY has monitored black carbon concentrations since the beginning of 2009. The annual concentrations are on average 0.7 μg/m3 (in Kallio) and at the highest they were 2.6 μg/m3 (monitored at Töölöntulli in 2010). In the clean background areas in the Southern Finland, the annual average was ca. 0.2−0.5 μg/m3. There is no reference or limit value for black carbon.