 To determine ΔH , many if not most of the air dispersion models developed between the late 1960s and the early 2000s used what are known as " the Briggs equations . " G. A. Briggs first published his plume rise observations and comparisons in 1965 . In 1968 , at a symposium sponsored by Conservation of Clean Air and Water in Europe , he compared many of the plume rise models then available in the literature . In that same year , Briggs also wrote the section of the publication edited by Slade dealing with the comparative analyses of plume rise models . That was followed in 1969 by his classical critical review of the entire plume rise literature , in which he proposed a set of plume rise equations which have become widely known as " the Briggs equations " . Subsequently , Briggs modified his 1969 plume rise equations in 1971 and in 1972 . 
