Study Finds Vapor Disappears Quicker Than Cigarette Smoke

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In a new study published by the Oxford Academic, researchers found that particles from e-cigarette vapor are much smaller and dissipate quicker than particles in cigarette smoke. These findings counter the misconception that secondhand vapor is the same as secondhand smoke and indicate that vaping has less of an effect on bystanders than smoking because its emissions disappear more quickly.

An international team of scientists created an experiment to study the concentration of particles emitted by vapor products compared to combustible cigarettes. In order to measure the difference, smokers and vapers were placed in relatively small rooms at different distances from a mannequin, which simulated a nearby bystander. The goal was to gauge how much a person would be affected by the particles.

They measured how long particles of smoke vs. vapor remained in the environment. They tested both closed and open systems of vapor products and created three different ventilation speeds in the room to simulate a variety of environments. The quantity of particles was measured using the Particle Number Concentration (PNC), which tracked the number of air particles over time.  

For vapor emissions, the researchers looked at two different distances between vaper and bystander. When the mannequin was close (.5 meters to 1 meter) there was a rapid increase in PNC of up to 10^6 particles/cm3 followed by a rapid decrease in PNC, reverting back to similar levels before exhalation. When the same experiment was conducted 2 meters from the mannequin, this shift of PNC barely even registered.

The rate of return back to pre-emission rate was also investigated. It took only 10 to 15 seconds for the air to revert back to PNC levels from before vaping exhalation. In contrast, the particles from combustible cigarettes took 30 to 40 minutes to revert back to the original rates.

The study also found that particles resulting from smoking were much larger than those in vapor. Combustible cigarette exhalation produced particles up to 300 nanometers (nm) whereas vapor produced particles of about 150 nm. These differences, the researchers said, came from vapor being produced from less stable liquid droplets and accounted for their quicker dissipation time.  

In their accompanying abstract, researchers concluded: “Significant differences between emissions from the tested e- and conventional cigarettes are reported. Exhaled e-cigarette particles are liquid droplets evaporating rapidly; conventional cigarette smoke particles are far more stable and linger.”

As with previous studies that looked at the effects of secondhand vapor, the takeaway has been that vapor products result in far fewer particles that remain for a much shorter span of time. This study adds to a list of scientific studies showing how vapor products and combustible cigarettes should not be treated as the same thing.

Read the study here: “Characterization of the Spatial and Temporal Dispersion Differences Between Exhaled E-Cigarette Mist and Cigarette Smoke”