Updated July 07, 2015.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Definition:
Mainstream smoke is the exhaled smoke released after taking a puff on a lit cigarette.

The composition of mainstream smoke is affected by how the smoker inhales and exhales, so it will vary from person to person. The frequency of puffs, duration and volume all contribute to the chemical makeup of mainstream smoke.

Mainstream smoke and sidestream smoke, which is the smoke wafting from the end of a lit cigarette, are the components of environmental tobacco smoke, also known as ETS.

See Also:  Secondhand Smoke Facts