All major air pollution incidents that have lead to documented elevated levels of human mortality have occurred during period of thermal inversions One of the most notable incidents of a thermal inversion occurred in London, England, on December 5, 1952. A thermal inversion developed enveloping the city in fog with essentially no vertical movement of air higher than 150 feet The sulfur dioxides and particulates from burning coal, in addition to the other pollutants of a large city, accumulated for four days During the four days, an estimated 4000 deaths occurred beyond those normally experienced for a four-day period Two similar episodes also occurred in 了oLER London in 1956 and 1962 This type of smog is now known as classic smogOne of the most notable incidents of a thermal inversion occurred in London, England, on December 5, 1952. A thermal inversion developed, enveloping the city in fog with essentially no vertical movement of air higher than 150 feet. The sulfur dioxides and particulates from burning coal, in addition to the other pollutants of a large city, accumulated for four days. During the four days, an estimated 4000 deaths occurred beyond those normally experienced for a four-day period. Two similar episodes also occurred in London in 1956 and 1962. This type of smog is now known as classic smog. All major air pollution incidents that have lead to documented elevated levels of human mortality have occurred during period of thermal inversions