Secondhand smoke is the smoke exhaled by the smoker.
Sidestream smoke is the smoke that rises off the end of a burning cigarette. Most of the smoke in a room is sidestream smoke. Sidestream smoke contains two or three times more harmful chemicals than secondhand smoke because it does not pass through the cigarette filter. At its worst, a child in a very smoky room for one hour with several smokers inhales as many bad chemicals as he would by actually smoking 10 or more cigarettes. In general, children of smoking mothers absorb more smoke into their bodies than children of smoking fathers because they spend more time with their mothers.