The major offender is paraffin scented candles. Paraffin is the predominant wax used in the candle industry. Paraffin is the final byproduct in the petroleum refining chain.

David Krause, an air quality engineer and former employee of the Florida Department of Health, says that the soot given off from the burning of paraffin candles is the same as that given off by burning diesel fuel. Some of the air contaminants in paraffin fumes include toluene, benzene, methyl ethyl ketene (MEK), and naphthalene--substances found in paint, lacquer and varnish removers.

The state of California, under its Proposition 65 Safe Drinking Water and Toxic Enforcement Act of 1986, has identified at least seven major toxins in paraffin wax including the carcinogen benzene.

The burning of scented candles produces even more contaminates then unscented paraffin candles alone. University of Michigan Scientists state that chemicals used in the paraffin, particularly the heavily scented ones emit known toxins, allergens and even carcinogens, like benzene, acetone, mercury, toluene and a host of other much harder to pronounce. These chemicals can be damaging to the cardiovascular, neurological and immune systems.

Since 1976, the Consumer Products Safety Commission has warned the candle industry about the dangers of lead based wicks. Presently, 30 percent of the candles on the market have lead core wicks. Lead and zinc are metals commonly used in the core of the wicks. The metal makes the wicks stand up straight making candle manufacturing easier.

If you want scent in the house, use pure essential oils with a diffuser (use a beeswax votive in the warmer) and avoid cheap air fresheners and even incense, which also release harmful soot.

Please, make sure that the wicks are all-cotton without a metallic core, your health depends on it.