The term “secondhand vape” refers to the exhaled cloud. This aerosol is a complex mixture of fine, airborne liquid droplets that are released into the surrounding air after a user takes a puff from an electronic cigarette. Understanding the duration of these suspended particles is important for assessing indoor air quality and potential bystander exposure. The time these particles remain airborne is determined almost entirely by their physical composition and the immediate environment.
The Physical Nature of the Aerosol
The aerosol cloud is generated by heating a liquid, commonly known as e-liquid, which typically contains propylene glycol (PG), vegetable glycerin (VG), flavorings, and often nicotine. When heated by the device’s coil, these components flash-evaporate and then rapidly cool upon mixing with ambient air, forming a dense cloud of microscopic liquid particles. Unlike smoke, which is composed of solid combustion byproducts, the e-cigarette aerosol consists of liquid droplets.
The size of these droplets is a primary factor in their fate, with the majority of particles falling into the ultrafine and submicron range, often measuring between 200 and 400 nanometers. Because the particles are liquid and highly volatile, they do not possess the same stability as solid smoke particles. This liquid composition means the droplets begin to evaporate almost immediately upon exhalation, turning back into gas-phase compounds.
Propylene glycol and vegetable glycerin are the main solvents that form the bulk of these liquid particles. The proportion of these two can affect the cloud’s density, as higher VG content tends to create a thicker, more persistent aerosol. Ultimately, the physical characteristics of the aerosol—its liquid nature and volatility—set it up for a short life suspended in the air.
Airborne Duration and Influencing Factors
The visible cloud of secondhand vape aerosol generally stays suspended in the air for a very brief period, typically lasting from a few seconds up to a few minutes. In a room with good air circulation, the visible aerosol often disperses within 10 to 30 seconds. This short duration is a direct consequence of the rapid evaporation of the volatile components.
The most influential factor governing this duration is the rate of air exchange, or ventilation. In a closed-off space with no airflow, the aerosol can linger for several minutes, creating a visible haze as the particles slowly settle. Conversely, opening a window, running a fan, or using an air purification system can cause the particles to dissipate almost instantly. Studies have shown that while the initial particle concentration can be high, it drops back to normal levels almost immediately when ventilation is active.
The power of the vaping device also plays a role in the initial hang time. High-powered, sub-ohm devices generate a denser cloud containing more liquid particles, which may take slightly longer to fully disperse. The total volume of the room and the overall air exchange rate are also relevant, as they determine the speed at which the airborne concentration is diluted. Even in smaller, enclosed environments like a car, the aerosol generally clears within one or two minutes, assuming some movement of air.
Beyond the Air: Surface Deposition
Once the aerosol particles have left the air, a portion of the non-volatile components deposits onto surrounding surfaces, creating a residue known as “thirdhand exposure.” This deposition occurs as the airborne liquid droplets settle out or as the gas-phase components condense onto cooler surfaces. The distinction between airborne secondhand exposure and surface-based thirdhand exposure is important.
The residue includes components like nicotine, heavy metals, and various flavor chemicals. Nicotine is one of the most commonly measured residues, as it readily adheres to surfaces like walls, furniture, and clothing. This chemical residue can persist long after the visible cloud has disappeared from the air.
Children and infants are considered particularly susceptible to this thirdhand exposure due to behaviors like crawling on floors and putting objects in their mouths, which increases contact with contaminated surfaces. The deposited nicotine and other substances can also react with other chemicals in the environment, potentially forming new compounds. Therefore, while the airborne phase is short, the chemical consequences of the aerosol on indoor surfaces can be long-lasting.
Contextualizing the Difference: Vape vs. Smoke
The fundamental difference between e-cigarette aerosol and traditional tobacco smoke lies in their physical and chemical origins. Tobacco smoke is the result of combustion, creating stable, non-volatile solid particles that linger in the air for extended periods in poorly ventilated spaces. In contrast, the e-cigarette aerosol is a product of heating, and its liquid droplets are highly volatile, causing them to evaporate and disperse rapidly.
This difference in stability means that secondhand vape aerosol particles are removed from the air primarily through evaporation, whereas traditional smoke particles must be physically removed by ventilation or gravitational settling. Chemically, the aerosol from e-cigarettes contains significantly lower levels of many harmful and potentially harmful constituents found in smoke.
When comparing the surface residue, the nicotine deposited on indoor surfaces from e-cigarette use is also significantly lower than the residue from traditional smoking. Nicotine residue levels from vaping have been measured to be nearly 200 times lower than those found in the homes of cigarette smokers.