Stratification 08 : The rising or settling of layers of smoke, according to density or weight, with the heaviest layer on the bottom; smoke layers usually collect from the ceiling down
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}