Table 1.

Aerosol generation and particle measurement devices suitable for e-liquids assessment.

Application	Name	Specifications	Commercial supplier
Aerosol generation	Vibrating Orifice Aerosol Generator 3450	Generates aerosols with E-liquids Generates particles from 1 to 200 μm Particles are uniform in size, shape, density	TSI http://www.tsi.com/
	Collison Nebulizer	Atomizes different E-liquid mixtures. Atomizes liquids and suspensions at different temperatures in control environment and generates stable aerosol output.	CH Technologies http://chtechusa.com/
	Vitrocell® Spiking System	Produces gas mixtures from solvents, gases, and vapors with a heating capability up to 400 °C	Vitrocell® systems http://www.vitrocell.com/
	Smoking Machines	Similar to its use in conventional cigarettes, can be applied to different e-cig devices connected directly. More recently, vapor producing instruments (smoking machines) suitable for e-cig devices are available.	Vitrocell® systems http://www.vitrocell.com/
	Condensation Monodisperse Aerosol Generator	Generates monodisperse aerosols by controlled condensation of vapors and suspensions. Generates aerodynamic diameter ranges from 0.1 μm to 8 μm (GSD <1.15)	TSI http://www.tsi.com/
Particle size measurement	Aerodynamic Particle Sizer	Capable of measuring: 0.5–20 μm 1 s time resolution Volume flow requirements: 5 L/minute Particle concentration range: 0.001–1000 (10,000) particles per cm3	TSI http://www.tsi.com/
	Fast Mobility Particle Sizer Spectrometer	Applicable for e-cigs and conventional cigarette. Capable of measuring: 6–560 nm 1 s time resolution Required volume flow: 10 L/minute Particle concentration range: no fixed value; depending on particle size and averaging time	TSI http://www.tsi.com/

Abbreviations: GSD: geometric standard deviation; ppb: parts per billion; ppm: parts per million.