Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer

<div><p>Objectives</p><p>To determine the effect of applied power settings, coil wetness conditions, and e-liquid compositions on the coil heating temperature for e-cigarettes with a “top-coil” clearomizer, and to make associations of coil conditions with emission of toxic carbonyl compounds by combining results herein with the literature.</p><p>Methods</p><p>The coil temperature of a second generation e-cigarette was measured at various applied power levels, coil conditions, and e-liquid compositions, including (1) measurements by thermocouple at three e-liquid fill levels (dry, wet-through-wick, and full-wet), three coil resistances (low, standard, and high), and four voltage settings (3–6 V) for multiple coils using propylene glycol (PG) as a test liquid; (2) measurements by thermocouple at additional degrees of coil wetness for a high resistance coil using PG; and (3) measurements by both thermocouple and infrared (IR) camera for high resistance coils using PG alone and a 1:1 (wt/wt) mixture of PG and glycerol (PG/GL).</p><p>Results</p><p>For single point thermocouple measurements with PG, coil temperatures ranged from 322 ‒ 1008°C, 145 ‒ 334°C, and 110 ‒ 185°C under dry, wet-through-wick, and full-wet conditions, respectively, for the total of 13 replaceable coil heads. For conditions measured with both a thermocouple and an IR camera, all thermocouple measurements were between the minimum and maximum across-coil IR camera measurements and equal to 74% ‒ 115% of the across-coil mean, depending on test conditions. The IR camera showed details of the non-uniform temperature distribution across heating coils. The large temperature variations under wet-through-wick conditions may explain the large variations in formaldehyde formation rate reported in the literature for such “top-coil” clearomizers.</p><p>Conclusions</p><p>This study established a simple and straight-forward protocol to systematically measure e-cigarette coil heating temperature under dry, wet-through-wick, and full-wet conditions. In addition to applied power, the composition of e-liquid, and the devices’ ability to efficiently deliver e-liquid to the heating coil are important product design factors effecting coil operating temperature. Precautionary temperature checks on e-cigarettes under manufacturer-recommended normal use conditions may help to reduce the health risks from exposure to toxic carbonyl emissions associated with coil overheating.</p></div

Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer - Fig 1

<p><b>Experimental setup for determination of coil heating temperature using a thermocouple and an infrared (IR) camera:</b> (A) typical position of the thermocouple on a coil head; and (B) details of the heating coil section (green box) from which minimum, mean, and maximum temperatures were determined using an IR camera.</p

Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer - Fig 6

<p><b>Comparison of thermocouple and infrared (IR) camera temperature measurements for coil HR #6 under the wet-through-wick condition: (A) 3 V; and (B) 6 V.</b> Note: HR = high resistance; button activation cycle = 4 s activation every 30 s; test liquid = 1:1 (wt/wt) mixture of propylene glycol and glycerol (PG/GL); see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195925#pone.0195925.g001" target="_blank">Fig 1</a> for measurement set-up.</p

Summary of temperature measurement conditions.

<p>Summary of temperature measurement conditions.</p

Peak heating temperature measured for different voltage settings, coil resistances, and e-liquid fill levels as a function of applied power.

<p>Note: button activation cycle = 4 s activation every 30 s; test liquid = propylene glycol.</p

Peak heating temperature measured for different e-liquid fill levels and e-liquid compositions as a function of voltage settting.

<p>Note: HR = high resistance; button activation cycle = 4 s activation every 30 s; test liquid = propylene glycol (PG) or a 1:1 (wt/wt) mixture of propylene glycol and glycerol (PG/GL).</p

Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer - Fig 4

<p><b>Peak heating temperature measured for coil HR #4 under various coil conditions: (A) 3 V; and (B) 6 V.</b> Note: HR = high resistance; button activation cycle = 4 s activation every 30 s; test liquid = propylene glycol.</p

Evaluation of gowns and coveralls used by medical personnel working with Ebola patients against simulated bodily fluids using an Elbow Lean Test

<p>Gowns and coveralls are important components of protective ensembles used during the management of known or suspected Ebola patients. In this study, an Elbow Lean Test was used to obtain a visual semi-quantitative measure of the resistance of medical protective garments to the penetration of two bodily fluid simulants. Tests were done on swatches of continuous and discontinuous regions of fabrics cut from five gowns and four coveralls at multiple elbow pressure levels (2–44 PSI). Swatches cut from the continuous regions of one gown and two coveralls did not have any strike-through. For discontinuous regions, only the same gown consistently resisted fluid strike-through. As hypothesized, with the exception of one garment, fluid strike-through increased with higher applied elbow pressure, was higher for lower fluid surface tension, and was higher for the discontinuous regions of the protective garments.</p