Incense is a combustible material composed of aromatic biomass, such as plant matter and essential oils, which releases fragrant smoke when burned. For centuries, people have used this smoke to create a pleasant atmosphere and mask odors indoors. The common perception is that this process purifies the air, linking the pleasant scent with a cleansing effect. The question remains whether this practice truly cleans the air or introduces new pollutants into the home environment.
Traditional Use of Incense for Purification
The practice of burning aromatic substances for purification is deeply rooted in human history and various cultural traditions. Many ancient civilizations employed incense in religious ceremonies and rituals, believing the smoke cleansed spiritual spaces. Frankincense and myrrh have been used for millennia not only for their scent but also for a perceived hygienic function, especially in crowded, pre-modern environments.
Historically, the strong, fragrant smoke served a practical purpose by effectively masking unpleasant smells. Beyond odor control, certain natural ingredients found in traditional incenses, such as sage or specific tree resins, were thought to ward off sickness. Some modern studies indicate that smoke from certain herbal incenses can temporarily reduce airborne bacterial counts in a closed room, lending support to the historical belief in its antimicrobial properties.
Chemical Composition of Incense Smoke
The combustion of any organic material, including incense, is a chemical process that releases numerous compounds into the atmosphere. Incense smoke is primarily a product of incomplete combustion, which generates two main categories of air pollutants.
Particulate Matter (PM)
The first category is Particulate Matter (PM), which consists of tiny solid and liquid droplets suspended in the air. Burning incense releases significant concentrations of fine particulate matter, known as PM2.5, which are particles less than 2.5 micrometers in diameter. These microscopic particles are small enough to penetrate deep into the human respiratory system. Studies show that incense can produce PM2.5 emission factors comparable to, or greater than, those produced by burning a cigarette.
Volatile Organic Compounds (VOCs)
The second category is Volatile Organic Compounds (VOCs), which are gases that vaporize at room temperature. Common VOCs identified in incense smoke include known toxins such as benzene, toluene, and formaldehyde. Other harmful compounds, including polycyclic aromatic hydrocarbons (PAHs) and various aldehydes, are also generated during the burning process. These pollutants mix into the indoor air, fundamentally changing its chemical makeup.
Impact on Indoor Air Quality and Health
Scientific measurements confirm that burning incense does not clean the air; rather, it significantly contributes to indoor air pollution. The concentration of PM2.5 in a room where incense is burned often rises to levels far exceeding safety guidelines established by the World Health Organization (WHO). These elevated pollutant levels can persist for a substantial time after the stick or cone has finished burning, especially in poorly ventilated spaces.
Exposure to high concentrations of PM2.5 is a major health concern because these fine particles can bypass the body’s natural defenses and enter the deepest parts of the lungs. In the short term, this exposure can trigger respiratory irritation, coughing, and exacerbate conditions like asthma. The VOCs released, particularly formaldehyde and benzene, are also irritants that can affect the eyes, nose, and throat.
Long-term exposure to incense smoke has been linked to more serious health outcomes, particularly among those who are exposed daily, such as workers in temples. The fine particulate matter and carcinogenic VOCs contribute to oxidative stress and inflammation throughout the body. This chronic exposure increases the risk of developing respiratory diseases, and studies have associated it with an increased incidence of cardiovascular issues, including coronary artery disease and stroke.
Minimizing Risks When Using Incense
For individuals who still wish to use incense, there are several practical steps to mitigate the documented risks to indoor air quality. The most effective action is to ensure proper and substantial ventilation during and after burning. Opening a window or using an exhaust fan helps to disperse the emitted PM2.5 and gaseous VOCs, preventing them from accumulating to hazardous concentrations.
Users should also limit the duration of burning and the number of sticks or cones used at one time. Burning incense for a shorter period introduces fewer pollutants into the environment. Choosing high-quality incense made from pure, natural ingredients may reduce the emission of certain synthetic or toxic compounds, though it does not eliminate the production of harmful particulate matter from the combustion process itself.