|This article is about an older version of DF.|
Where there's smoke, there's fire.
When items burn, they release smoke into the surrounding area. The presence of smoke means that it is reasonably close to a source of fire, which can cause fun times. Like miasma, smoke can easily cross z-levels up or down through openings. If you see smoke, you have (or very recently had) a fire burning somewhere nearby and should take action. (Since fire is deadly and can easily spread, this is bad enough by itself.)
Dwarves that inhale smoke will get unhappy thoughts. They also may get internal injuries or become unconscious.
Most materials have boiling points, and you will occasionally see things like steam or boiling clouds of copper, especially if you're playing with magma. If you accidentally drop some coal or coke into magma, you get generic smoke.
Minor testing has indicated that smoke, from the moment the source disappears, takes approximately 7 seconds to dissipate. This dissipation is noticeable as the smoke tile will change many times throughout this interval, indicating the smoke's drop in density. If smoke seems to persist for more than this time it is possible there is an unseen source or that a Bug has been encountered.[Verify]