Friability

Substances that are designated hazardous, such as asbestos and crystalline silica, are often said to be friable if small particles are easily dislodged and become airborne, and hence respirable (able to enter human lungs), thereby posing a health hazard.

Tougher substances, such as concrete, may also be mechanically ground down and reduced to finely divided mineral dust. However, such substances are not generally considered friable because of the degree of difficulty involved in breaking the substance's chemical bonds through mechanical means. Some substances, such as polyurethane foams, show an increase in friability with exposure to ultraviolet radiation, as in sunlight.

Friable is sometimes used metaphorically to describe "brittle" personalities who can be "rubbed" by seemingly-minor stimuli to produce extreme emotional responses.

General

A friable substance is any substance that can be reduced to fibers or finer particles by the action of a small amount of pressure or friction, such as rubbing or inadvertently brushing up against the substance. The term could also apply to any material that exhibits these properties, such as:

• Ionically bound substances that are less than 1 kg/L in density
• Clay tablets
• Crackers
• Mineral fibers
• Polyurethane (foam)
• Aerogel