A particulate filter lowers soot, making this engine ULEV certified. Burning surface oil can also be a source for pollution such as soot particles. Carbon is released in the normal incomplete combustion reaction, forming soot and dust. Like all activities involving combustion, fossil-fuel-powered aircraft release soot and other pollutants into the atmosphere. New particulate filters can capture from 30% to greater than 95% of the harmful soot. Kibera is heavily polluted by human refuse, garbage, soot, dust, and other wastes. Inorganic salts present on the surface of the soot particles may make them hydrophilic. Coal and soot or carbon black are informally called amorphous carbon. The chimney must be swept to remove the soot. Least significant on a mass basis is the release of soot and sulfate particles. London was noisy and its air was full of soot from countless coal fires. Regeneration is the process of burning off (oxidizing) the accumulated soot from the filter. The pigment bistre was made from beech wood soot. The formation of soot depends strongly on the fuel composition. It is less effective for other anthropogenic influences like soot.