Most of us know something about second hand smoke. But have you heard of third hand smoke? It's the contaminants tobacco smoke leaves behind.

When you burn tobacco leaves, lots of chemicals are released, such as tar and nicotine. They can linger on clothes, hair, upholstery, carpets and drapes long after the smoke has cleared from the air.

But the list of chemicals go far beyond tar and nicotine. If you look at the additives allowed in the manufacture of cigarettes, you'll find about 600 possible ingredients. Once you burn the cigarette, those ingredients release over 4,000 chemicals, of which about 40 are carcinogens – meaning they cause cancer.

Other chemicals in the smoke can also react with chemicals already in the air to create additional carcinogens. For example, nicotine can react with nitrous acid to create a potent carcinogen called nicotine–derived nitrosamine ketone or NNK.

Since nicotine can linger in the air for days or months, that's plenty of time for the conversion to happen.

For smokers who believe by smoking outside, they're not contaminating their home, they're wrong.

Residual smoke can linger in a smoker's lungs two to three minutes after the last exhalation and then be released when they go back inside.

Children are particularly susceptible to third hand smoke and can absorb these carcinogens through their skin or by ingesting them. It's sobering to learn that one out of every five deaths is related to smoking.

Each year, a staggering 440,000 people die in the US from tobacco use.

What third hand smoke tells us is that it's very difficult, if not impossible, for smokers to create smoke free environments. So if not for your own health, then for the health of your family, especially your kids... don't smoke at all.