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Cigarette combustion science


Over the last 50 years a substantial understanding of the physics and chemistry underlying cigarette combusion and the formation of tobacco smoke has been generated, along with characterisation of some of the main smoke toxicants[1-2].

The current state of knowledge in these areas has been summarised in a number of reviews and book chapters[3-7]. In a series of publications in the 1980's, Dr Richard R. Baker systematically established the distributions of combustion temperature, gas velocity and key smoke constituents inside a burning cigarette[8-11]. These have become the foundation of modern cigarette combustion science. Based on Dr Baker’s and other studies in the literature, the following is a schematic representation of the key thermophysical processes occurring inside and around a burning cigarette:


Briefly, when a smoker draws on a lit cigarette, the temperature of the cigarette coal rises rapidly from its resting (smouldering) temperature of around 600 °C.  Peak puff  temperatures at the periphery of the coal can exceed 900 °C during a 35 mL, 2-sec puff. The high temperature inside the coal causes an increase in the viscosity of the air flowing through and a concomitant increase in the resistance to the draw of air through the coal.  This effect forces air to be drawn primarily into the periphery of the coal around the paper burn line, which causes more complete combustion in this peripheral region. 

X-ray combustion images

The depletion of oxygen due to combustion results in the formation of a region immediately behind the coal where the temperatures remain high enough for thermal decomposition of tobacco (the pyrolysis/distillation zone).  Large amounts of volatile and semi-volatile smoke constituents are produced in this region. A small amount of air is drawn in along the tobacco rod through permeable cigarette paper and smoke temperature decreases rapidly to produce a supersaturated aerosol. The smoke thus formed during a puff is subjected to filtration by the remaining tobacco rod and cigarette filter, as well as dilution by any filter ventilation holes. Some proportion of the light gases (such as CO) will diffuse out of the highly permeable cigarette paper. The smoke that leaves the mouth end of the cigarette is called mainstream smoke.  Between puffs, hot smoke escapes from the top of the cigarette and forms the sidestream smoke.

Some of our recent combustion studies have focused on understanding the interactions between a burning cigarette and cellulosic substrates that make up the bands used to manufacture cigaretttes aimed at reducing the ignition propensity of the cigarette as measured by the American Standard ASTM 2187-04[12-14]. In addition, we have been performing pyrolysis experiments under simulated cigarette burning conditions to investigate both the mechanistic and also kinetic aspects of tobacco or tobacco ingredients combustion[15-21]. Re-newed attempts are also being made to model a burning cigarette using modern computational tools[22,23].

More than 5,000 smoke constituents have so far been identified in cigarette smoke[7].  Around 150 of these have been identified as smoke toxicants. Over the last 20 years researchers and public health organisations, including Health Canada, have drawn up toxicant lists comprising sub-sets of these constituents - the most widely cited being the ‘Hoffmann Analyte’ list of 44 constituents.  Cigarette combustion science will remain to play an important role in understanding the formation of smoke constituents.  We have research underway to seek to deternine which of these toxicants are likely to be most important in relation to the various smoking-related diseases.

  1. Wynder, E., Hoffmann D. (1967). Tobacco and tobacco smoke – studies in experimental carcinogenesis. New York and London: Academic Press.
  2. Norman, A. (1999). Smoke Chemistry. In: D. Layten Davis & Mark T. Nielsen. Eds. Tobacco Producton, Chemistry and Technology. Oxford: Blackwell Science Ltd. pp. 353-387.
  3. Baker, R. R. (1999). Smoke chemistry. In: D. Layten Davis & Mark T. Nielsen. Eds. Tobacco Production, Chemistry and Technology. Oxford: Blackwell Science Ltd. pp. 398-439.
  4. Baker, R. R. (2005). Smoke generation inside a burning cigarette. Paper presented at the 9th International Congress on Combustion By-Products and their Health Effects, Tucson, Arizona, USA, June 12-15.
  5. Baker, R.R. (2006). Smoke generation inside a burning cigarette: modifying combustion to develop cigarettes that may be less hazardous to health. Prog. Energy. Combust. Sci. 32(4): 373-385 
  6. Borgerding, M., Klaus, H. (2005). Analysis of complex mixtures – cigarette smoke. Experimental & Toxicologic Pathology, 57 (S1): 43-73.
  7. Rodgman, A., Perfetti, T.A. (2008). The chemical components of tobacco and tobacco smoke. USA: Taylor and Francis Ltd.
  8. Baker, R.R., Kilburn, K.D. (1973). The distribution of gases within the combustion coal of a cigarette. Beitr. Tabakforsch. 7: 79-87.
  9. Baker, R.R. (1974). Temperature distribution inside a burning cigarette. Nature. 247: 405-406 .
  10. Baker, R.R. (1975). Temperature variation within a cigarette combustion coal during the smoking cycle. High. Temp. Science. 7: 236-247.
  11. Baker, R.R. (1976). Gas velocities inside a burning cigarette. Nature. 264: 167-169. 
  12. Liu, C. (2005). The ASTM 2187-02b standard method on testing cigarette ignition propensity, Paper presented at CORESTA Smoke Science and Product Technology Meeting, Stratford-upon-Avon, UK, September 2005, Paper SSPT 13, CORESTA CD-ROM No. 21.
  13. Kellogg, D.S., Waymack, B.E., McRae, D.D., Chen, P., Dwyer, R.W. (1998). The initiation of smoldering combustion in cellulosic fabrics. J. Fire Sci. 16: 105-124.
  14. Lewis, L.S., Townsend, D.E., Robinson, A.L. (1990). A comparative ignition propensity study of foreign and U.S. cigarettes. J. Fire Sci. 8: 239-253.
  15. Baker, R. R. (1983). Formation of carbon oxides during tobacco combustion: pyrolysis studies in the presence of isotopic gases to elucidate reaction sequence. 
  16. Baker, R. R. (1987). Keynote review: Some burning problems in tobacco science. Proceedings of The International Conference on the Physical and Chemical Processes Occurring in a Burning Cigarette, Winston-Salem, North Carolina, USA, April 26-29, 1987.
  17. Torikai, K., Yoshida, S., Takahashi, H. (2004). Effects of temperature, atmosphere and pH on the generation of smoke compounds during tobacco pyrolysis. Food and Chem. Toxicol. 42: 1409-1417.
  18. Torikai, K., Uwano, Y., Nakamori, T., Tarora, W., Takahashi, W. (2005). Study of tobacco components involved in the pyrolytic generation of selected smoke constituents. Food and Chem. Toxicol. 43: 559-568.
  19. Czegeny, Z., Blazso, M., Varhegy, G., Jakab, E., Liu, C., Nappi, L. (2009). Formation of selected toxicants from tobacco under different pyrolysis conditions. Journal of Analytical and Applied Pyrolysis. 4 (4): 297-334 
  20. Varhegy, G., Czegeny, Z., Jakab, E., McAdam, K.G., Liu, C. (2009). A TGA study of tobacco combustion assuming DAEM devolatilization and empirical char burn-off kinetics. J. Anal. Appl. Pyrolysis. 86: 310-322 
  21. Varhegy, G., Czegeny, Z., Liu, C., McAdam, K.G. (2009). Thermogravimetric analysis of tobacco combustion assuming DAEM devolatilization and empirical char-burnoff kinetics. Ind. Eng. Chem. Res., 2010, 49 (4), pp 1591–1599. 
  22. Eitzinger B. (2006). A simulation study of self-extinguishing cigarettes. Beitr. Tabakforsch. Int. 22: 79-87.
  23. Rostami, A.A., Murthy, J., Hajaligol, M. (2003). Modeling of a smouldering cigarette. J. Anal. Appl. Pyrolysis. 66(1): 281-301.
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