Internal contour distributions for gas temperatures and for the concentrations of carbon monoxide, carbon dioxide, hydrogen, propane and oxygen have been determined at successive times before, during and after a puff of a burning cigarette. The cigarette was smoked in an atmosphere of 21% (v/v) oxygen in argon. The gases were withdrawn from the cigarette through a small sampling probe and filtration unit, and analyzed using a quadrupole mass spectrometer. The contour distributions show that the gas formation and transmission processes occurring in the coal, and their variation during the smoking regime, are complex. The interior of the coal is almost entirely devoid of oxygen. The consumption of oxygen is so rapid that the position of its major influx into the coal, near the paper burn line, cannot be seen on the contour diagrams during a puff. However, the oxygen influx during the puff leaves burnt-out channels in the coal which become evident at later stages in the smoking cycles. When the puff ends, the product formation/transfer balance is interrupted resulting in a local build-up of the product in its formation region. This local build-up up reaches a maximum at 0.5-1.0 seconds after the end of the puff, after which time diffusion processes deplete the level. During the static smoulder period, distinct high and low temperature regions for the formation of carbon monoxide and dioxide are not evident inside the coal. However, towards the latter half of the puff, a distinct carbon dioxide formation region starts to appear behind the completely oxygen-deficient region. Application of the pyrolysis computer model, developed previously, confirms that this second region is a thermal decomposition region, and shows that such a region for carbon monoxide is not resolved from the combustion region.