FIGURE 4.

Three-dimensional quantitative modelling results of the gas (CO₂) concentration distribution in an in vitro exposure system chamber: a) real-time CO₂ concentration distribution over 5 s exposure of smoke (initial CO₂ concentration modelled at 1.0 mol·L⁻¹) showing a gentle gas distribution in the exposure chamber; b) real-time CO₂ concentration distribution over 5 s exposure of fresh air (the initial CO₂ concentration was the final CO₂ concentration in the exposure chamber from the previous smoke exposure and it was assumed that there was no CO₂ in the fresh air exposed to the chamber); c) volume average concentration of CO₂ in the chamber for one smoke–fresh air cycle would lead to a drop in CO₂ concentration in the chamber back to zero; and d) average outlet concentration of CO₂ after one smoke–fresh air cycle confirming that exposure kinetics were sufficient to reach a repeatable smoke–air exposure cycle (zero concentration at the outlet).