Electronic nicotine delivery systems (ENDS) and heated tobacco products (HTPs) generate aerosol without the heat used for termination in machine smoking. Therefore, termination systems using the aerosol’s optical density have been developed. Since both ENDS and HTPs can be vaped on the same machine, a flexible end-point detection system is required to accommodate both types of product, either to terminate vaping or to prompt product exchange in continuous vaping systems.

Our objective was to develop a system to provide both real-time and recorded characteristics of aerosol production of ENDS and HTPs with an in-built calibration capability to reliably define the termination setting. This can be configured with a puff engine as a stand-alone bench-top unit or integrated into a multi-channel vaping machine.

Aerosol density is sensed via optical fibres set at the outlet of the product. The source intensity is normalised by channel before each run. A graphical interface presents real-time information and sets the termination level. The peak opacity after each puff is recorded and signals are set at user-defined ‘be prepared’ and ‘end-of-life’ levels. The system can also characterise aerosol production where there is electronic control of product lifetime.

HTP aerosol is less dense than that of ENDS and tends not to follow a gentle decline over life. Puff-to-puff noise can be significant for ENDS, such that a simple trigger level underestimates product life. Intensity calibration significantly reduces channel-to-channel variation. We have previously demonstrated that cumulative opacity can be linked to aerosol yield and this is available to the user.

Detection of the optical density of the aerosol can define end-of-life and is also capable of providing yield information that is useful for R&D and QA. In-built calibration enhances the flexibility of the system, particularly where a wide range of products and product types are vaped.