Heat-not-burn (HNB) is a category of tobacco product that heats real tobacco to a temperature high enough to release nicotine and flavor but low enough to avoid combustion. Where a lit cigarette burns tobacco at over 900°C, HNB devices operate between 250°C and 350°C. That single difference in temperature is the core idea behind the technology, and it changes the chemical profile of what the user inhales.
How the Devices Work
An HNB device is a small, battery-powered unit that accepts a specially manufactured tobacco stick, sometimes called a “heat stick” or “neo stick.” The stick contains a plug of reconstituted tobacco leaf rather than the loose-cut tobacco found in a conventional cigarette. Once inserted, the device heats the tobacco for a limited session, typically around 6 minutes or 14 puffs before it shuts off automatically.
Two main heating methods exist. Earlier devices, like IQOS 3, use a small metal blade that penetrates the tobacco stick and heats it through electrical resistance, reaching about 340°C. Newer models, like IQOS ILUMA, use induction heating, where a magnetic field heats a metallic element embedded inside the tobacco stick itself, eliminating the blade entirely. Another major product, the Kent glo, uses a heated chamber that surrounds the stick and reaches roughly 245°C. The result in all cases is an aerosol, not smoke, that the user inhales.
What Changes When Tobacco Doesn’t Burn
Burning tobacco at 900°C triggers thousands of chemical reactions that produce tar, carbon monoxide, and a long list of compounds classified as harmful or potentially harmful. Lowering the temperature substantially reduces, but does not eliminate, these byproducts.
In machine-based lab testing, HNB emissions contained at least 98% less carbon monoxide than cigarette smoke. Levels of other harmful compounds dropped by at least 62%. Tar reduction was more modest, with some products showing only a 21% decrease and others cutting tar by more than half, depending on the device and testing method. Nicotine delivery also varied, ranging from about 18% to 73% of the nicotine found in cigarette smoke. So while HNB products are not nicotine-free, they generally deliver less nicotine per session than a combustible cigarette.
It’s worth noting that “reduced” does not mean “zero.” The aerosol still contains nicotine, some carbonyls, some phenols, and other compounds. The question for public health is whether those reductions translate into meaningfully lower risk over years of use.
What the Health Research Shows So Far
Short-term cardiovascular studies paint a mixed picture. In a study of 22 current smokers with no existing health conditions, using an HNB product raised heart rate, blood pressure, and arterial stiffness by amounts similar to smoking a conventional cigarette. All of those measures were significantly elevated from baseline, suggesting the acute cardiovascular hit is comparable.
Oxidative stress tells a slightly different story. A crossover trial exposed 20 smokers to combustible cigarettes, e-cigarettes, and HNB products. All three raised markers of oxidative stress and reduced blood vessel function compared to baseline. However, HNB products produced less oxidative stress than both e-cigarettes and traditional cigarettes, and less blood vessel dysfunction than traditional cigarettes. Lab studies on mouse cells showed the same pattern: HNB aerosol increased oxidative damage in a dose-dependent way, but less so than cigarette smoke.
No long-term epidemiological data exist yet, because these products have not been widely used for long enough to study outcomes like lung cancer or heart disease over decades.
Indoor Air and Secondhand Exposure
Because HNB devices produce an aerosol rather than sidestream smoke, indoor air quality is less affected than with cigarettes. Testing in simulated office, residential, and hospitality settings found that only two substances rose above background levels: nicotine and acetaldehyde. Nicotine concentrations in the air ranged from 0.66 to 1.81 micrograms per cubic meter depending on the room type. Formaldehyde, a notable concern with cigarette smoke, did not rise above background levels during HNB use in these tests.
That said, bystanders are still exposed to low levels of nicotine and at least one irritant compound. The exposure is dramatically lower than secondhand cigarette smoke, but it is not zero.
FDA Authorization and Regulatory Status
In July 2020, the U.S. Food and Drug Administration authorized the IQOS system as a “modified risk tobacco product,” a designation that allows specific marketing claims about reduced exposure to harmful chemicals. A second authorization for the IQOS 3 system followed in March 2022. This is a narrow regulatory category. The FDA authorization means the agency reviewed evidence that switching completely from cigarettes to IQOS reduces exposure to certain harmful substances. It does not mean the product is safe, and the authorization explicitly does not claim reduced disease risk.
Outside the U.S., HNB products are sold in dozens of countries, with Japan and parts of Europe being the largest markets. Regulations vary widely: some countries treat HNB products like cigarettes, others classify them separately, and a few have banned them outright.
Maintenance and Residue Buildup
Manufacturers typically recommend cleaning the device after every 20 sticks. Residue does accumulate in the heating chamber, and researchers initially hypothesized that reheating that buildup could release additional toxicants. Testing focused on carbonyls and phenols found no significant difference in emissions between a freshly cleaned device and one used for 20 sticks without cleaning. What did affect emissions was how the user puffed: longer puff duration, higher flow rate, and more puffs per session all increased toxicant output more than residue buildup did. Researchers have noted, though, that other compounds like polycyclic aromatic hydrocarbons have not been fully assessed for the residue effect.
Environmental Considerations
HNB sticks create waste similar to cigarette butts, with an added layer of electronic waste from the devices themselves. In Japan, the largest HNB market, manufacturers have set up collection programs through retailers for used devices, batteries, cartridges, and capsules, largely because of fire safety risks from lithium-ion batteries. These programs do not, however, cover the used tobacco sticks, which are discarded like conventional cigarette waste. The sticks contain reconstituted tobacco, a filter segment, and various wrapping materials, none of which are widely recyclable through existing systems.
How HNB Compares to Vaping
HNB and e-cigarettes both avoid combustion, but they work differently. E-cigarettes heat a liquid solution containing nicotine, while HNB devices heat actual tobacco leaf material. This distinction matters because the aerosol chemistry differs. HNB aerosol contains tobacco-specific compounds that e-cigarette vapor does not, simply because real tobacco is involved. On the other hand, e-cigarettes can contain compounds produced by heating the liquid’s carrier ingredients, which HNB products lack. Both categories sit between combustible cigarettes and complete abstinence on the risk spectrum, but they are not interchangeable products and their long-term risk profiles may diverge as more data become available.