Austin Close1, Jane Blackerby1, Heather Tunnell2, Jack Pender2, Eric Soule  3, Sinan Sousan  This email address is being protected from spambots. You need JavaScript enabled to view it.1,4 

1 Department of Public Health, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
2 Department of Chemistry, East Carolina University, Greenville, NC 27858, USA
3 Department of Health Education and Promotion, College of Health and Human Performance, East Carolina University, Greenville, NC 27858, USA
4 North Carolina Agromedicine Institute, Greenville, NC 27834, USA

Received: January 12, 2023
Revised: June 27, 2023
Accepted: July 21, 2023

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Close, A., Blackerby, J., Tunnell, H., Pender, J., Soule, E., Sousan, S. (2023). Effects of E-Cigarette Liquid Ratios on the Gravimetric Filter Correction Factors and Real-Time Measurements. Aerosol Air Qual. Res. 23, 230011.


  • Mixtures of propylene glycol (PG) and vegetable glycerin (VG) were prepared.
  • The effects of PG/VG ratios used in electronic cigarettes (ECIGs) were evaluated.
  • Five PG/VG ratios were aerosolized using a SMOK Novo 2 ECIG brand and a pump.
  • Aerosol concentrations were inversely proportional at higher PG content.
  • Different instrument filter correction factors are needed at higher PG content.


Electronic cigarettes (ECIGs) generate high concentrations of particulate matter (PM), impacting the air quality inhaled by humans through secondhand exposure. ECIG liquids are available commercially and some users create their own “do-it-yourself” liquids, and these liquids often vary in the amounts of their chemical ingredients, including propylene glycol (PG) and vegetable glycerin (VG). Previous studies have quantified PM concentrations in ECIG aerosol generated from liquids containing different PG/VG ratios. However, the effects of these ratios on aerosol instrument filter correction factors needed to measure PM concentrations accurately have not been assessed. Thus, ECIG aerosol filter correction factors for multiple aerosol instruments (SMPS + APS, MiniWRAS, pDR, and SidePak) were determined for five different PG/VG ratios 1) 0PG/100VG, 2) 15PG/85VG, 3) 50PG/50VG, 4) 72PG/28VG, and 5) 90PG/10VG and two different PM sizes, PM1 (1 µm and smaller) and PM2.5 (2.5 µm and smaller). ECIG aerosols were generated inside a controlled exposure chamber using a diaphragm pump and a refillable ECIG device for all the ratios. In addition, the aerosol size distribution and mass median diameter were measured for all five ECIG ratios. PM2.5 correction factors (5–7.6) for ratios 1, 2, 3, and 4 were similar for the SMPS + APS combined data, and ratios 1, 2, 3 were similar for the MiniWRAS (~2), pDR (~0.5), and SidePak (~0.24). These data suggest different correction factors may need to be developed for aerosol generated from ECIGs with high PG content. The higher correction factor values for the 90PG/10VG ratio may have resulted from greater PG volatility relative to VG and sensor losses. The correction factors (ratios 1–4) for PM2.5 were SMPS + APS data (4.96–7.62), MiniWRAS (2.02–3.64), pDR (0.50–1.07), and SidePak (0.22–0.40). These data can help improve ECIG aerosol measurement accuracy for different ECIG mixture ratios.

Keywords: Particulate matter, PM2.5, ECIG, PG/VG ratios, Filter correction factors

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