British American Tobacco has developed a whole smoke exposure system to investigate and assess toxicity of cigarette smoke to human lung epithelial cells exposed at the air-liquid interface. Cigarette smoke is generated and diluted using a Borgwaldt RM20S smoking machine and delivered to a small (188cm3), clear Perspex™ exposure chamber, which houses cells supported on commercially available inserts. In this study we have assessed smoke loss/deposition within the tubing of our whole smoke exposure system. An electrical mobility spectrometer was used to measure cigarette smoke particulates at three points in the system: after smoke generation, at delivery to the chamber and at the exhaust from the chamber. We conducted a three-way comparison of different tubing types in the RM20S including polyurethane (conditioned and new) and Viton®. Results indicated that 76-90% of particulates reached the chamber with 18-39% being deposited in the chamber. Minimal losses were observed using conditioned polyurethane tubing.