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.

      This demonstration will allow you to see the significant differences between burning the tobacco in a cigarette compared to the tobacco vapor generated when tobacco is heated in Platform 1. 

      We will start the demonstration by inserting a tobacco stick into the Platform 1 holder and placing it as well as the cigarette in the aerosol demo machine. 

      The Platform 1 holder is turned on and the cigarette is lit. 

      The tobacco vapor and cigarette smoke will go through the glass tubes. And the tobacco vapor and cigarette smoke will be captured on the white colored laboratory filter pads. 

      Both the cigarette and tobacco stick contain tobacco. 

      However, when a cigarette is lit, the tobacco is set on fire and burns, reaching temperatures of above 600 °C. 

      This burning process generates smoke and ash. 

      When a smoker takes a puff, this temperature rises above 800 °C at the burning tip. 

      On the other hand, Platform 1 uses a heating blade to heat the tobacco to no more than 350 °C.

      At these temperatures the tobacco does not burn and no smoke or ash is formed.

      Heating tobacco with Platform 1 generates a tobacco vapor that is not smoke. 

      Looking at the glass tubes, you can see smoke from a cigarette in one and tobacco vapor from Platform 1 in the other. 

      You will notice a difference in the color of cigarette smoke in the back formed when burning tobacco compared to the color of tobacco vapor in the front formed when tobacco is heated in Platform 1.

      What you cannot see is that both the cigarette smoke and Platform 1 tobacco vapor contain levels of harmful and potentially harmful constituents.

      But because Platform 1 heats tobacco instead of burning it, it produces a tobacco vapor that provides a real tobacco taste and satisfaction with an average reduction in the levels of harmful and potentially harmful constituents of 95% compared to cigarette smoke. 

      In addition, unlike cigarette smoke, there is no formation of solid particles in the tobacco vapor generated by Platform 1 since there is no combustion of the tobacco. 

      Now that the demonstration has finished, we can compare the two laboratory filter pads.

      Based on the scientific evidence so far, switching completely to Platform 1 presents less risk to your health than continuing to smoke cigarettes and therefore it is a better choice than smoking cigarettes.

      It is very important to remember that Platform 1 is not risk free. 

      It uses tobacco sticks that contain nicotine which is addictive. 

      The best choice is to quit tobacco and nicotine use altogether. 

      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.

      Combustion only occurs when there are three main elements: fuel, heat, and oxygen. When even one element is removed, combustion stops. Most toxicants in cigarette smoke are released through combustion, so by eliminating combustion, we can potentially reduce the level of toxicants in the aerosol compared to cigarette smoke.

      In this video we will demonstrate that a cigarette combusts while Platform 1 does not, by putting each of them in an enclosed environment filled with air, then nitrogen gas. 

      First, we’ll remove the left lid of the Combustion Demo machine – designed for use with a cigarette. Then we’ll light a cigarette, place it in the lid, and re-attach the lid to the central chamber. 

      Air supply from a tank is switched on and channeled into the central chamber through this tube on the right.  

      Then, we place a finger over the opening of the right lid to create a seal which increases the pressure in the chamber, filling it with the air supply and simulating a puff being drawn from the cigarette. 

      Here, you can see that the cigarette produces mainstream smoke, and sidestream smoke. 

      A cigarette reaches temperature above 600 degrees Celsius, which is hot enough to sustain combustion. And when a smoker takes a puff, the tip of a cigarette can reach over 800 degrees Celsius.

      Turning the switch changes the input from air to nitrogen. After a few puffs, air in the chamber is replaced by nitrogen, which removes oxygen from the combustion equation. 

      As you can see, the mainstream and sidestream smoke begin to clear, because combustion has stopped. When we remove the cigarette, you can see this clearer.

      To compare, we’ll carry out this demo with Platform 1. This time, we’re removing the right lid of the Combustion Demo machine – designed for use with Platform 1 – putting a tobacco stick into the Platform 1 holder, then switching it on. Platform 1 is placed in the right lid of the machine and re-attached to the central chamber. 

      Once again, when we switch on the air supply, air is fed into the Combustion Demo machine. Then we place a thumb over the opening of the left lid to draw puffs. Note that there is only mainstream aerosol being created from the mouthpiece.

      When we switch from air to nitrogen, there’s no change: Platform 1 continues to work. That’s a major difference, compared to the cigarette.  

      Since oxygen is found in air, when we replace air with nitrogen, it removes oxygen from the equation. If combustion occurred in Platform 1, it would have stopped producing aerosol similar to the cigarette earlier. 

      But as you can see, Platform 1 is still producing aerosol, because it heats tobacco to no more than 350 degrees Celsius, which is not enough heat for combustion to occur. This shows that a cigarette combusts while Platform 1 does not.  
      Our scientific evidence has shown that Platform 1 aerosol contains an average of 95% lower levels of toxicants than the reference cigarette smoke. This, however, does not mean a 95% reduction in risk.

      While Platform 1 is not risk free and it delivers nicotine, which is addictive. Based on the totality of our available evidence, switching completely to Platform 1 is less harmful than continuing to smoke. 

      This video is used herein for illustration of concepts only, with no commercial purpose. All concepts are aimed exclusively at adult smokers. It is very important to remember that Platform 1 is not risk free. It uses tobacco sticks that contain nicotine, which is addictive. The best choice is to quit tobacco and nicotine use altogether.

      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.