Cigarette combustion: Why it is the major problem with smoking

      Learn how cigarette combustion releases high levels of harmful chemicals, and why switching to smoke-free products from Philip Morris International (PMI) may reduce the harmful effects of smoking.

      What is combustion?

      In traditional cigarettes, the combustion process involves the burning of tobacco, leading to temperatures above 400 °C—often reaching 800 °C and more at the tip—and the production of cigarette smoke.

      Combustion is defined as a self-sustaining chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or flame. For combustion to occur, three things need to be present: a fuel to be burned, a source of oxygen, and a source of heat. Combustion also includes both complete and incomplete (partial) combustion processes, such as smoldering (flameless) and flaming combustion.

      Cigarette smoke is a result of combustion. During the combustion process, particulate matters are formed when products of combustion and high-temperature pyrolysis reach high enough concentration to nucleate via condensation, or when they interact with each other to form liquid particulate matter (droplets) and solid particulate matter (soot). Although smoke is an aerosol, this mix of gases, liquid droplets, and solid particles formed during combustion is what makes smoke different from other aerosols.

      Burning tobacco creates high levels of harmful chemicals

      Cigarette smoke has been well characterized, with more than 6,000 chemicals identified, and among those, about 100 have been identified by public health authorities to be associated with smoking-related diseases such as lung cancer, heart disease, and emphysema. These chemicals are known as harmful and potentially harmful constituents (HPHCs), such as carbon monoxide (CO).

      Nicotine is also found in cigarette smoke. While nicotine is addictive and not risk free, nicotine is not the primary cause of smoking-related diseases but is one of the reasons people smoke cigarettes.

      Unlike common misconceptions, combustion does not release tar as it is not a chemical, but a weight measurement of a portion of the smoke produced by a cigarette. Read more about cigarette tar.

      For more information about tobacco smoke and the HPHCs contained within it:

      Quitting tobacco and nicotine altogether is always the best choice for any smoker. However, we know that most smokers continue to smoke. Scientifically substantiated smoke-free products have a potentially valuable role to play in reducing the harm from cigarette smoking, as they emit or release much lower levels of HPHCs than cigarettes.

      Heat-not-burn products

      Heat-not-burn (HnB) products, also referred to as heated tobacco products (HTPs), are a category of products that heat the tobacco instead of burning it, with the aim of significantly reducing the emission of HPHCs that are associated with combustion compared with cigarettes.

      HnB products typically consist of an electronic device and a heated unit containing tobacco. This innovative and evolving category includes products that vary with respect to temperature, heating source, and the way the tobacco is processed (e.g., dry, moist, or tobacco extracts).

      At PMI, we use various technologies to heat the tobacco. These include resistive heating technology which can be used internally, directly within the tobacco plug via a heating blade (or pin), or externally via a flexible resistive heating surrounding the tobacco stick. We have also developed induction technology which employs a magnetitic field to heat up the tobacco substrate from within.

      Aerosol demo

      Heating vs Burning

      This aerosol demonstration visually demonstrates the difference between the aerosol from our tobacco heating system (THS), our leading HnB product, and cigarette smoke. We see that THS produces an aerosol which contains significantly less constituents compared with cigarette smoke, making it a better choice for adults who don’t quit than smoking.

      Note, "Platform 1" in this video refers to THS

      What are the differences between HnB products and cigarettes?

      Unlike cigarettes which burn the tobacco, HnB products are designed to heat the tobacco, producing an aerosol which, if scientifically substantiated contains significantly fewer and lower levels of HPHCs compared with smoke from cigarettes. Through our studies, we have already demonstrated that our leading HnB product, the Tobacco Heating System (THS), generates far fewer and lower levels of HPHCs, making adult smokers who switch to THS less exposed to harmful chemicals.

      In addition, HnB products are different from cigarettes in that they do not produce secondhand smoke. Due to the lack of combustion HnB products generate an aerosol, which is not some, hence no secondhand smoke is generated. In addition, we have done studies on the impact of the use of our HnB products on indoor air quality and our findings indicate that, because these products do not produce smoke, they do not have a negative impact on indoor air quality.

      Read some of our research on the impact of THS use on indoor air quality:

      Scientific evidence that our HnB products do not burn tobacco

      We use heat control technologies in our HnB products to ensure that the tobacco does not reach the temperatures necessary for combustion to occur. The absence of combustion in THS has been substantiated by scientific evidence and has been verified by third-party scientific experts in numerous countries as well as by independent research organizations. Furthermore, the comparison of the chemical composition of THS aerosol generated in oxidative (air) and non-oxidative (nitrogen) environments indicates that oxygen—necessary for combustion to happen—does not play a role in the operation of THS.

      Combustion demo

      Oxygen not required

      This combustion demonstration illustrates that combustion occurs in cigarettes but not in THS, our leading HnB product. By removing oxygen, cigarette combustion stops, while THS continues to produce aerosol. Scientific evidence shows that our THS aerosol contains significantly lower levels of toxicants compared with cigarette smoke, but it is not risk free. A growing number of scientific studies indicate that switching completely to THS has the potential to be significantly less harmful than continuing to smoke.

      Note, "Platform 1" in this video refers to THS

      E-cigarettes or e-vapor products and combustion

      Within our portfolio of smoke-free products, we offer a range of e-cigarettes, also known as e-vapor or vaping products. E-cigarettes are handheld battery-operated devices that heat an e-liquid that generally, but not always, contains nicotine. 


      Is there combustion in e-cigarettes?

      E-cigarettes, also known as e-vapor products, do not burn tobacco, and in fact do not contain tobacco at all, so there is no combustion. While they are not risk free, for adults who would otherwise continue smoking, e-cigarettes are a better alternative to cigarettes because unlike smoking, there is no burning of tobacco and therefore no production of smoke. Instead, our e-cigarettes use various technologies, such as wick and coil or ceramic heater technology, to heat up a specially formulated e-liquid to produce an aerosol that contains significantly lower levels of HPHCs compared with cigarette smoke.

      PMI’s smoke-free products do not burn tobacco

      There is a growing scientific consensus that completely switching to tobacco or nicotine-containing products that do not burn tobacco has the potential to present less risk of harm than continued smoking for adult smokers who don't quit. Learn more about our smoke-free products, read an overview of what we've learned from our research on these products, or you can go straight to our publications library for all the scientific details.