Increased complaints regarding blackened carpets , baseboards , plastic switch plates, kitchen appliances and tellevision screens, as well as dark lines on ceilings and walls have prompted several recent investigations. The furnace/air handler is usually blamed. Upon inspection, the air handlers are generally found to be doing what they are designed to do: pull air into the return, condition the air , then return the conditioned air to the living space. Of course, anything in the air will be pulled in and redistributed through the duct system.
Investigation has shown that soot produced by scented candles, jar candles and oil candles are the likely cause of these black stains.In the last 5 years the candle industry has doubled as demand has increased. Candles are now mass produced, using what is suspected to be lower grade waxes and material that result in a higher oil content. These candles produce more soot when burned.
In a test by Engineer Ron Baily in Palm Beach Gardens, Florida, four candles were burnt for a total of 15 hours. These candles produced so much soot in the home that the testers were forced to stop for fear of creating too much damage in the house."We had significant soot production on the walls, drapes, dishwasher, refrigerator, and the A/C filter."
Bailey explained that there are two issues to consider when looking at how a candle might soot."The length, thickness, and strength of the wick highly influence how a candle burns, and also what is in the candle wax itself." Today the growing trend is in the use of aromatic candles. Fragrance added to the wax should be specifically for use in candles. The high temperatures can cause chemicals to behave differently once burned. "Five percent paraffin wax is good," said Bailey."But with many of the candles in stores today, we find a mixture of materials, including some fragrances that were not intended for this use." The mixture of the various fragrances and chemicals can result in a candle that is going to burn dirtier than expected.
Most filters used in furnace/air handlers are not capable of removing the ultra fine soot produced by candles. When confronted with a claim of a furnace/air suspcted of causing sooting in the home, check first for the use of candles in the home.Courtesy from Lennox Industries July 1, 1998