Vapor Density 06 : The ratio of the average molecular weight of a given volume of a gas or vapor to the average molecular weight of an equal volume of air at the same temperature and pressure
Ingenieurbro Frank Markmann, Fire, Arson & Explosion Investigation in Germany and Europe, Fire Investigators Dictionary (The English definitions 1995 Edition of NFPA 921 Guide for Fire and Explosion Investigation), Wald, Germany (Revised 2008), http://www.fmfire.de/fidicteg.html, (FrInv - Brit) {94}