Smoke
Overview
Smoke is a mixture of solid and liquid particulates and gases generated when materials combust. It primarily consists of carbon particles (soot), tar, water vapor, carbon dioxide, carbon monoxide, and others, and is produced more abundantly under conditions of incomplete combustion. Smoke is both a sign of fire and a major cause of air pollution, capable of severely affecting human health and the environment.
Main Content
Principles of Smoke Generation
Smoke is generated when fuel does not react sufficiently with oxygen. Complete combustion produces only carbon dioxide and water, while incomplete combustion releases carbon monoxide, soot, and various organic compounds. The composition of smoke varies greatly depending on the type of fuel (wood, petroleum, plastic, etc.), temperature, and oxygen supply. For example, wood smoke mainly contains levoglucosan and tar, which are decomposition products of cellulose, while petroleum smoke is rich in polycyclic aromatic hydrocarbons (PAHs).
Physical Properties of Smoke
Smoke exists in the form of aerosols with particle sizes ranging from 0.01 to 10 μm. These particles scatter light, causing smoke to appear white, black, or gray. White smoke primarily consists of water vapor and fine droplets (e.g., fog), while black smoke indicates a high content of carbon particles. The density of smoke is lower than that of surrounding air, so it tends to rise, but it can also linger near the ground when cooled.
Chemical Composition of Smoke
Smoke can contain thousands of chemical substances. Major components include carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NOx), sulfur oxides (SOx), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), formaldehyde, and acrolein. Notably, PAHs and formaldehyde are known carcinogens. Additionally, smoke contains a large amount of fine particulate matter (PM2.5), which causes respiratory diseases.
Smoke and Health
Inhalation of smoke causes both acute and chronic health problems. Acute exposure can lead to coughing, difficulty breathing, eye irritation, headaches, and dizziness, and in severe cases, carbon monoxide poisoning can be fatal. Chronic exposure increases the risk of lung cancer, chronic obstructive pulmonary disease (COPD), and cardiovascular diseases. Particularly, long-term exposure to wildfire smoke or tobacco smoke has serious health impacts. The World Health Organization (WHO) classifies fine particulate matter in smoke as a Group 1 carcinogen.
Smoke and the Environment
Smoke is a major contributor to air pollution, playing a role in the formation of smog and acid rain. Smoke from wildfires or fossil fuel combustion lingers in the atmosphere for a long time and also affects climate change. Black carbon in smoke absorbs solar radiation, accelerating global warming. Furthermore, smoke can hinder plant photosynthesis and disrupt material cycles in ecosystems.
Industrial Uses of Smoke
Despite its negative impacts, smoke is utilized in various fields. Smoking is a traditional method for food preservation and flavor enhancement. Smoke is also used in firefighting training, special effects (film and theater), military smoke screens, and pesticide fumigation. Recently, research is underway to extract useful compounds from smoke for use as pharmaceutical or fragrance raw materials.
Smoke Detection and Fire Prevention
Smoke detectors are widely used for early fire detection. Ionization detectors operate on the principle that smoke particles interfere with ion currents, while photoelectric detectors sense light scattering caused by smoke. Modern buildings are equipped with smoke control systems to secure evacuation routes during fires. Additionally, satellite-based smoke monitoring systems have been developed for wildfire prediction.
Recent Trends
As of 2024–2025, research and technology related to smoke are advancing in three main directions. First, studies on the health impacts of wildfire smoke are actively ongoing. As large wildfires increase due to climate change, analysis of the air quality and human effects of long-range transported smoke is being strengthened. Second, smoke filtration technology is becoming more advanced. Air purifiers combining HEPA and activated carbon filters, as well as personal smoke masks (e.g., N95), have improved in performance. Third, real-time sensor technology for detecting hazardous substances in smoke has developed, leading to the proliferation of smartphone-compatible air quality monitors. Additionally, AI-based smoke dispersion prediction models are being developed and used for fire response.
Related Topics
- [[Air pollution]]
- [[Fire]]
- [[Particulate matter]]
- [[Carbon monoxide poisoning]]
- [[Wildfire]]