The study objective was to develop and validate a smoking analyser device able to record the puffing topography of e-cigarette users. The Smoking Analyser Number 7 (SA7) (British American Tobacco) was modified to overcome issues caused by the condensation of humectants in the topography head, which led to inaccurate puff volume determinations using the existing SA7 design.

The device was first calibrated against known pressure and flow rates in the ranges of 0-120 mmWG and 2-120 mL/sec, respectively, using a calibrated pressure meter and A14 syringe driver (Borgwaldt). The calibrated output demonstrated linearity over these ranges.

The modified device demonstrated equivalence to the original SA7 when tested across a range of puff volumes, durations and profiles (sine, square and triangle). Puff volumes were on average within ±0.1 mL of the pre-set volume across the range 20-80 mL, whilst puff durations were within ±0.01 s of the duration measured using the original SA7 device, in the range 1.5-3.0 s.

The performance of the modified device to accurately record puffing topography profiles of e-cigarettes was evaluated using disposable, cartomiser based and modular devices, puffed to exhaustion of the e-cigarette battery or a maximum of 150 puffs. Each e-cigarette was tested in triplicate at three pre-defined puffing regimes across flow rates of 18.3-40.0 mL/s and produced puff volumes within 8.2% (4.5 mL) of the pre-set values. The degree of accuracy observed for puff volume measurements of the e-cigarette aerosols is comparable to the 6.0% level observed for combustible cigarette aerosol measurements.

We propose that the modification to the existing SA7 technology provides a robust system for the measurement of e-cigarette users’ puffing topography. We provide examples of users' puffing behaviour, as a first step in providing data to support evaluation of e-cigarettes in a manner reflective of users’ behaviour.