Abstract
Many Electronic Nicotine Delivery Systems (ENDS) employ integrated sensors to detect user puffing behavior and activate the heating coil to initiate aerosol generation. The minimum puff flow rate and duration at which the ENDS device begins to generate aerosol are important parameters in quantifying the viable operating envelope of the device and are essential to formulating a design of experiments for comprehensive emissions characterization. An accurate and unbiased method for quantifying the flow condition operating envelope of ENDS is needed to quantify product characteristics across research laboratories. This study reports an accurate, unbiased method for measuring the minimum and maximum aerosolization puff flow rate and duration of seven pod-style, four pen-style and two disposable ENDS. The minimum aerosolization flow rate ranged from 2.5 to 23 (mL/s) and the minimum aerosolization duration ranged from 0.5 to 1.0 (s) across the ENDS studied. The maximum aerosolization flow rate was defined to be when the onset of liquid aspiration was evident, at flow rates ranging from 50 to 88 (mL/s). Results are presented which provide preliminary estimates for the effective maximum aerosolization flow rate and duration envelope of each ENDS. The variation in operating envelope observed between ENDS products of differing design by various manufacturers has implications for development of standardized emissions testing protocols and data reporting required for regulatory approval of new products.
Highlights
There is little consistency in puffing regimes being used for Electronic Nicotine Delivery Systems (ENDS) emission studies; studies have used 15 ml/s, 4 s puffs [1], 27 ml/s, 3 s puffs [49], 39 ml/s, 1.8 s puffs [2], 27.5 ml/s, 2 s puffs [3, 4], 17.5 ml/s 2 s puffs [5,6,7], 10 ml/s, 4 s puffs [8], and in some articles the puffing protocol is unclear [9, 10]
Selected operator and analyst annotations regarding the minimum aerosolization flow rate (MinAF) and maximum aerosolization flow rate (MaxAF) are presented on the figure
We found the nicotine mass ratio to be largely independent of puff flow rate, duration, and volume by conducting a multi-variate linear regression analysis of fNic for all 13 products
Summary
There is little consistency in puffing regimes being used for ENDS emission studies; studies have used 15 ml/s, 4 s puffs [1], 27 ml/s, 3 s puffs [49], 39 ml/s, 1.8 s puffs [2], 27.5 ml/s, 2 s puffs [3, 4], 17.5 ml/s 2 s puffs [5,6,7], 10 ml/s, 4 s puffs [8], and in some articles the puffing protocol is unclear [9, 10]. Recent vaping machine standards [36] provide some basis for product comparisons, and do not reflect the range of use behavior anticipated in the natural environment. Yield terms, such as YTPM, are normalized “per puff,” while mass concentration terms, such as CTPM, are normalized by the puff volume expressed in (mg/mL). The lack of standardization has made it difficult to compare products across studies or make inferences about the impact of product characteristics on emissions
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