Tobacco smoke is a complex and dynamic matrix consisting of gaseous compounds and particulate material, in which about 4800 constituents have been identified (Baker, 1999). Smoke particles are sub-micron and their high concentration (typically 109 particles/cc) and the hygroscopic nature of the smoke droplets means that this particle diameter may change rapidly via coagulation and condensation (Ingebrethsen, 1986; McRae, 1990). The chemical composition and partition between both phases of the smoke is equally complex, can change continuously and is strongly influenced by time, temperature, chemistry and dilution of smoke. Despite the small diameter of the smoke particles, smoke deposition efficiencies of 60 – 80% in the lung have been reported (Baker & Dixon, 2006).
