Why Does a Candle Emit Smoke?
The primary cause of a candle emitting smoke is the incomplete chemical reaction known as combustion, of the wax or fuel, from which the candle is made. When the candle burns, the wax, which consists mainly of Hydrogen and Carbon molecules linked together in what is referred to as a Hydrocarbon chain reacts with the Oxygen in the surrounding air. This reaction (combustion) is what results in the production of heat, light, water vapour and carbon dioxide.
In the event of incomplete combustion, the result can be the formation of byproducts which can include unburned wax, carbon particles and volatile organic compounds referred to as VOC’s. These byproducts can present themselves as visible smoke when they condense in the cooler parts of the flame or surrounding air.
Factors contributing to incomplete combustion and thus smoke production
- Airflow - should there be insufficient air (oxygen) available to the flame; combustion will be incomplete, resulting in the production of smoke.
- Wax – The quality and type of wax used in a candle can have a significant effect on combustion. Some waxes may contain impurities (other than hydrogen and carbon) and additives which may lead to smoke production.
- Wick quality and length – Should the wick be too long, more wax than the flame can vapourise and burn efficiently can be drawn up through capillary action into the flame. This excess liquid wax can result in smoky combustion.
- Drafts – Drafts or turbulence around the candle may disrupt the flame’s stability and prevent proper combustion which can cause it to smoke.
- Candle design – The size and shape of the candle and container, including the size of the wick, will affect how well the candle burns and whether it produces smoke or not.
Steps to take to minimize smoke emission from candles
- Ensure the wick is trimmed to the appropriate length before lighting the candle – cotton wicks = 1/4 inch
- Maintain proper ventilation so there is sufficient oxygen provided for combustion
- Shield burning candles from drafts and air currents
- Ensure candles are well designed, with wicks suitable for their size and composition
- Select quality candles made with clean burning wax