A well-made candle, such as one from Fisher Creek Candles, should create virtually no smoke when burning properly. But there are certain instances when any candle can cause smoke or soot. If the wick is too long, or a draft disturbs the flame, small amounts of unburned carbon particles or soot will escape from the flame as a wisp of smoke. Any candle can do this if the flame is disturbed.
We use only flat cotton, lead free wicks with thin interwoven paper threads in all of our candles. This enhances the self-trimming effect and reduces mushrooming, soot, and smoke. Self-trimming means that the wick will burn itself down significantly so that you do not get the "mushroom" effect on the tip of the wick when you extinguish your flame. It takes care of some of the work for you. However, to prevent any smoke from coming from your candle you should always trim the wick to 1/4 inch before every use and be sure to place candles away from drafts, vents, or air currents. If a candle continually flickers or smokes, then it is not burning properly and needs to be extinguished. Let the candle cool completely, trim the wick, make sure the area is free from any drafts, and relight the candle.
Candle soot is not harmful. The small amount of soot produced by a candle is the natural byproduct of incomplete combustion. Candle soot is composed primarily of elemental carbon particles, and is similar to the soot given off by kitchen toasters and cooking oils. These everyday household sources of soot are not considered a health concern, and are chemically different from the soot formed by the burning of diesel fuel, coal, gasoline, etc.