Normal smoke is a gray/white smoke that is just the byproducts of combustion and includes some soot. In the cold weather, the water vapor, also a byproduct of combustion, appears as "white smoke".

Smoke from unburnt fuel can be white smoke if the fuel doesn't combust properly due to low compression or poor atomization. It can also be black smoke if it combusts incompletely due to insufficient air.

Smoke from a crackhead has a distinctive pungent aroma that can be noticed by anyone within 20 feet of the crackhead. One may also notice the crackhead doing some strange behaviors while smoke is being emitted.