Choosing between scented candles and wax melts involves understanding how each product releases fragrance and impacts indoor air quality. Scented candles use a wick and an open flame, triggering combustion to melt the wax and vaporize the fragrance oil. Since the burning is often incomplete, especially with flickering flames, this process generates various byproducts released into the surrounding air.
Wax melts are wickless and use an external heat source, such as an electric warmer, to melt the wax via conduction. This method avoids combustion entirely, as the wax is only heated to a melting point, typically a lower temperature than a candle flame. The fragrance is released when the heated wax evaporates the scent molecules without the chemical reactions involved in burning. This difference in operation is the primary factor influencing the emissions profile of each product.
Physical Emissions: Soot and Particulate Matter
The use of a flame in scented candles directly causes soot and fine particulate matter (PM) emissions. Soot consists of tiny black particles of carbon and aerosolized chemicals resulting from incomplete combustion. This fine particulate matter, including particles smaller than 2.5 micrometers (PM2.5), is a health concern because it can be inhaled deep into the lungs and potentially enter the bloodstream.
Wax melts use an electric warmer or gentle heat source, eliminating the wick and flame. Consequently, these products eliminate the generation of carbon soot and visible particulate matter. For consumers concerned with the solid byproducts of burning, such as black marks on walls or respiratory irritation, the wax melt offers a cleaner alternative.
Gaseous Emissions: Volatile Organic Compounds
Volatile Organic Compounds (VOCs) are chemical gases released into the air by both heated wax melts and burning candles. These compounds vaporize easily at room temperature and are the mechanism by which fragrance is delivered, but they also include chemicals like formaldehyde and benzene. The primary source of VOCs is the fragrance oil itself, meaning synthetic fragrances in both candles and melts can release these chemicals regardless of the delivery system.
Paraffin wax, which is a petroleum-derived substance, can release trace amounts of VOCs when burned or heated, but the scent chemicals are the major contributor. Scented wax melts can sometimes release a greater quantity of VOCs than traditional candles due to their higher fragrance concentration and larger surface area maximizing evaporation. Furthermore, VOCs like terpenes, commonly found in fragrances, can react with ozone in the indoor air to form new, extremely small nanoparticles. These nanoparticles can penetrate deep into the respiratory tract.
Minimizing Risk and the Healthier Choice
The question of which product is “healthier” depends on which type of pollutant a consumer wishes to avoid. Wax melts are generally a better choice for eliminating the risks associated with an open flame and the resulting soot and particulate matter. However, the absence of a flame does not mean the absence of air quality concerns, as highly scented wax melts can generate high concentrations of VOCs and secondary nanoparticles.
To minimize exposure to indoor air pollutants, consumers should focus on the product ingredients rather than just the delivery method. Selecting products made with natural waxes, such as soy or beeswax, may offer a cleaner option, though the fragrance remains the main source of concern. Consumers can significantly reduce VOC and nanoparticle exposure by choosing fragrance-free products or those scented only with pure essential oils. No matter the product chosen, ensuring good ventilation in the area of use will help dissipate any released emissions.