1952 65438+February 5 ~ 8, the soot incident in London, England, killed 4000 people. People call the smoke of this disaster "the smoke of killing". According to the analysis, this is because there was no wind and fog in London, and the smoke and dust generated by factory chimneys and residents' heating permeated the urban area of London for a long time. The highest concentration of smoke and dust reaches 4.46 mg/m3, and the daily average concentration of sulfur dioxide reaches 3.83 ml/m3. Sulfuric acid droplets produced by chemical reaction of sulfur dioxide attach to smoke or condense on fog droplets, and enter organs with breathing, which makes people sick or accelerates the death of patients with chronic diseases.