Second Hand Vapor

By Dr. Annie Macpherson
Updated: 2019-09-17


With very little research into the long term effects of second-hand vapor, we still don’t know how vaping indoors or in public places could affect people around you.

Whilst experts agree vaping is far less harmful than smoking, and vaping can help you quit, we know that vaping is not entirely harm free. Because vaping is not entirely harmless, the health of others unwillingly exposed to 2nd hand vapor needs to be considered.

In this article,

  1. We’ll explain why vapor is different to smoke, and whether there are any known health concerns we should consider on the issue of inhaling 2nd hand vapor.

What is Vapor?

E-cigarette vapor is considered by experts to be around 95% less harmful than cigarette smoke [1]. This is because vapor is a very different substance to smoke.

When liquids reach a critical temperature, that is lower than their point of combustion (or setting alight), they will boil and evaporate into a gas – for example, the water vapor produced when boiling a kettle. Unlike burning a compound, no new substances are formed in the vaporisation process.

When you take a drag from an e-cigarette, the e-juice is converted into a vapor. Just like steam, the compounds found in e-cigarette vapor are the same as those found in the un-vaporised substance – in this case, e-liquid.

It is important to remember that it is an urban myth that e-cigarettes produce ‘harmless water vapor’. E-cigarettes produce a gaseous version of the e-liquid a user is vaping.

E-cigarettes produce a vapor that is far more similar to water vapor than it is to smoke, but it is certainly not steam.

Is Vapor Different to Smoke?


The scientific term for burning, generates thousands of new, toxic substances in the form of smoke, entirely different from the initial substance that was burned.

Asides from delivering you nicotine, and looking similar when exhaled, smoke and vapor are entirely different substances. The 2nd hand vapor and smoke have very different effects on the people around you.

Smoke from cigarettes kills, and second-hand smoke is known to contain carcinogens and toxic substances. However, e-cigarettes do not burn, so there is no smoke, meaning there is also no second-hand smoke. However, there is second-hand vapor.

What is 2nd Hand Vapor?

Although experts know that vaping is far less dangerous than smoking and far less likely to kill you, we don’t know the full effects of secondhand vapor.

The vapor inhaled and exhaled from an e-cigarette contains trace amounts of nicotine and food-grade flavorings, suspended in a base vapor of either propylene glycol (PG) or vegetable glycerin (VG).

Is 2nd Hand Vapor Harmful?

Although second-hand vapor is certainly less harmful to others than second-hand smoke, it seems as though it might carry some potential to have effects on your health, particularly children. The ultra-fine particle size of second-hand vapor means it can be considered a lung irritant.

Ultra-fine particulates from 2nd hand vapor carry the potentialto trigger or somebody else’s existing asthma near you worse in the short term [2].

A report investigating lung function of entertainment industry workers showed that individuals working for extended periods of time near ‘smoke machines’, producing volumes of PG vapor, had reduced lung function compared to others [3]. This suggests that exposure to PG vapor over long periods can affect your lung function.

However, when you are exposed to 2nd hand vapor, it is most likely a short term exposure that you will not experience again for a long time, which is relatively harmless. It’s not entirely comparable to this study, where individuals were exposed to PG vapor for up to four hours at a time.

Vaping Indoors

A small study from 2014 also discovered that using e-cigarettes indoors compromised air quality, by increasing the amount of particulates, nicotine and aluminium in the air. Each of these compounds has been linked to heart disease, cancer and lung diseases like asthma.

Again, this is not direct evidence, but it suggests 2nd hand vapor has some potential to have harmful effects on others, if they face long term exposures [4].

PG is commonly used as a base for e-liquids and is the main component of 2nd hand vapor. A 2010 study showed that young children exposed long-term to PG from fresh paint and cleaning solutions in their air inside their homes were much more likely to get asthma.

This means that if you are vaping a lot in confined spaces, PG-based second-hand vapor may have an effect on very young children, and potentially induce asthma [5]. There is no direct research or evidence relating childhood asthma cases to parents that vape indoors at the moment, but this early evidence is important to consider when vaping around young children.

Is Vapor Smoke Harmful?

Some people refer to the vapor from e-cigarettes as ‘vapor smoke’. This is an incorrect term that is misleading.

Vapor and smoke are different things

  • E-cigarettes produce vapor, and;
  • Burning tobacco produces smoke.

E-cigarettes are also known as vaporisers.

At short or low level exposures, it’s safe to assume second-hand vapor is relatively harmless.

It is only when someone is exposed long term to 2nd hand vapor that they might experience some short-term effects on their lung function.


If you are frequently using an e-cigarette indoors or in an poorly ventilated area around others, you might be exposing people to 2nd hand vapor for extended periods of time. Long exposures to PG vapor can induce asthma-like symptoms in young children and reduced lung function in adults, so it is always best to vape in a well ventilated environment or outdoors where possible, particularly when you are with children. Although no evidence has linked 2nd hand vapor to these health effects, and short term exposures are relatively harmless, it is certainly not unreasonable to consider others around you, particularly pregnant women and children, and avoid vaping in confined spaces.


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Dr. Annie Macpherson
Dr. Annie Macpherson

Annie has a PhD in Genome Stability from the University of Sussex. She has first-hand experience in cancer and human disease research. This allows her to provide us with new and unbiased insights into the ongoing research of the public and health effects of vaping. She loves an adventure, and has travelled through South East Asia and Australia working for Vaping Insider.