Smoke consists of finely divided solid and liquid particles suspended (held) in a gas. Smoke is mostly made up of carbon particles produced by the burning of fuel. Smoke particles are tiny and penetrate easily into the lungs to cause serious damage. Smoke also blackens buildings, corrodes metals, and damages vegetation, causing serious economic losses. Smoke has a few helpful uses. These include preserving meats, producing colored military signals, and protecting orchards with smudge pots during freezes. Smoke may become dangerously concentrated during a weather condition called thermal inversion. This condition occurs when a layer of warm air settles over a layer of cooler air that lies near the ground. The warm air traps the cool air and prevents the smoke from rising and scattering. See also Air pollution ; Environmental pollution .
