How Does Heat Not Burn Actually Work? The Chemistry
Around 350°C instead of 900°C changes what comes off a tobacco stick. What combustion contributes, what survives without it, and what is still unknown.
Quick answer
Heat-not-burn devices warm tobacco to roughly 250 to 350°C instead of the roughly 900°C at a burning cigarette tip. Without combustion, much less carbon monoxide and smoke is produced, but thermal breakdown of tobacco still releases nicotine and harmful compounds. The WHO notes some toxicants appear at higher levels than in cigarette smoke.
The phrase does describe something real. A heated tobacco device genuinely does not set tobacco on fire, and that genuinely changes what comes off it.
It is also doing rhetorical work, because “not burning” is not the same as “not producing harmful chemicals”, and the distance between those two statements is where most of the confusion in this category lives.
What combustion actually contributes
A lit cigarette is a small, extremely inefficient chemical reactor. The tip sits around 600°C while smouldering and can reach roughly 900°C during a draw. At those temperatures, tobacco does not simply release what was already in it. Molecules break apart and recombine into thousands of new compounds, which is why cigarette smoke is estimated to contain around 7,000 chemicals, some 70 of which are known carcinogens.
Three things follow from combustion specifically:
- Carbon monoxide, produced by incomplete burning and responsible for a meaningful part of smoking’s cardiovascular effect.
- Smoke, the visible product of a flame front, carrying solid particulate.
- Very large numbers of pyrolysis and combustion products created by the high temperature itself rather than present in the leaf.
Remove the flame and you remove most of the first two, and a substantial portion of the third. That is a genuine, measurable difference, and it is not in dispute.
350°C versus 900°C
Heated tobacco devices hold the stick in a working range of roughly 250 to 350°C, well below the ignition point of tobacco. The heat comes from a blade inserted into the stick, an induction-heated element built into it, or a chamber surrounding it, depending on the system.
The stick itself is not simply shredded tobacco. It contains processed, reconstituted tobacco plus an aerosol former, usually glycerine. That is important: the visible cloud is mostly glycerine-derived droplets carrying nicotine and other constituents, in the same broad way a vape produces its aerosol. The tobacco is what is being extracted; the glycerine is what carries it.
The result is an aerosol, not a vapour and not smoke. Aerosol is the accurate word: fine liquid droplets suspended in air. Water vapour is not what you are exhaling.
What survives without combustion
Here is the part the temperature comparison tends to obscure.
Nicotine. Entirely intact and delivered efficiently. Published pharmacokinetic work puts heated tobacco nicotine delivery at most of the way to a cigarette. Nothing about the heating method reduces it, and it is the reason the dependence is comparable.
Compounds already present in the leaf. Tobacco-specific nitrosamines exist in cured tobacco before anything is heated. Lower temperatures reduce their transfer, they do not eliminate their presence.
Thermal degradation products. This is the point that “not burning” hides. Combustion is not the only chemistry heat causes. Pyrolysis — the breakdown of organic material by heat in the absence of enough oxygen to burn — happens comfortably within the 250 to 350°C range. Compounds such as formaldehyde, acetaldehyde and acrolein appear in heated tobacco aerosol in measurements from both manufacturer and independent laboratories, at reduced levels compared with cigarette smoke but not at zero.
Ultrafine particles. Present, and small enough to reach deep into the airways.
The WHO’s information on heated tobacco products states that the aerosol contains toxic chemicals, including carcinogens, and — the sentence people most often skip — that levels of some substances are higher in heated tobacco aerosol than in cigarette smoke. Not most. Some. The overall profile is lower on most measured compounds, and it is not uniformly lower.
The distinction that matters most
If you retain one thing from this article, retain this.
Reduced exposure is not the same as reduced risk. The WHO has stated the point explicitly: reducing exposure to harmful chemicals in heated tobacco products has not been demonstrated to translate into reduced harm in humans.
That is not scepticism about the measurements. The measurements are mostly real; a well-run laboratory can compare aerosol to smoke and produce lower figures for a long list of compounds. The gap is between chemistry and outcomes. Disease risk from tobacco is not a linear function of any single measured toxicant. Cardiovascular risk in particular rises steeply at low exposures and then flattens, which is why light smoking carries much more risk than the reduction in cigarettes would suggest. A product that cuts several exposures by a large percentage may cut risk by considerably less.
Add the timescale. Tobacco-related disease is measured over decades. Heated tobacco has existed at scale for less than one, and the products have changed generation to generation within that time. Nobody, in any direction, has long-term outcome data on it. Anyone who tells you it is proven safer, and anyone who tells you it is proven equally harmful, is going beyond what exists.
This is also why the funding of a study is worth checking. A substantial share of the published chemistry comes from manufacturers, which does not make it wrong, but independent replication is what carries weight in a young field, and there is less of it than the category’s age would suggest.
What it means for you, in plain terms
Strip out the temperature debate and three things are solidly established.
- You are still taking in nicotine, at a level broadly comparable to a cigarette, so the dependence continues on the same terms.
- You are inhaling an aerosol containing toxicants, fewer than in smoke, more than none.
- Nobody can tell you what a decade of it does, because the decade has not happened yet.
The most useful consequence of all this is undramatic. The only variable you control with certainty is how many sticks you get through, because that scales everything above it. Not the heating method, not the brand, not the generation — the count.
Puff Counter, free to start and rated 5.0 on the App Store, exists for that one variable: one tap per stick, with next week’s ceiling built from the average you actually logged rather than the one you intended.
Today’s two minutes
The chemistry will keep being argued about for years. Your number will not.
Count today’s sticks. Every one, logged as it happens, changing nothing. Do it again tomorrow and the day after. Whatever the science eventually concludes about heat-not-burn aerosol, a lower number is better than a higher one under every version of the answer, and three days from now you will know exactly which number you are working with.
Frequently asked questions
What temperature does heated tobacco reach?
Manufacturers state a working range of roughly 250 to 350°C, well below the ignition point of tobacco. A lit cigarette reaches around 600°C while smouldering and up to roughly 900°C during a draw. That gap is the entire technical basis for the heat-not-burn category.
Is heated tobacco aerosol just water vapour?
No. It is an aerosol, meaning fine liquid droplets suspended in air, formed largely from glycerine added to the tobacco stick plus compounds released from the leaf. It carries nicotine and other chemicals, and calling it vapour describes how it looks rather than what it contains.
Does heat not burn remove tar?
Tar is defined as the particulate matter in cigarette smoke after nicotine and water are removed, so a product with no smoke has no tar by that definition. It still produces a particulate aerosol containing many of the same chemical families, which is why the absence of tar is a definitional point rather than a health guarantee.
If there is no combustion, why are harmful chemicals still present?
Because combustion is not the only chemistry that heat causes. Pyrolysis and thermal degradation break tobacco constituents down well below ignition, and tobacco-specific compounds present in the leaf transfer into the aerosol regardless. Fewer combustion products does not mean an absence of harmful ones.
