Pictogram 1: Flame - Pyrophorics

Pyrophorics are classified under Pictogram 1, the Flame pictogram. The HCS definition for a pyrophoric chemical is "a chemical that will ignite spontaneously in air at a temperature of 130° Fahrenheit (54.4° Celsius) or below." This means that the chemical can catch fire without an ignition source when the chemical is exposed to air.

Only a few elements have this ability to ignite spontaneously, such as lithium, powdered aluminum, and magnesium. Other chemicals that can ignite spontaneously in air are organometallic compounds, such as lithium hydride, diethyl zinc, and arsine. Compounds that have a bond of at least one metal to one carbon are organometallic compounds.

Pyrophorics can be in solid, liquid, or gas form. Pyrophoric solids and liquids are defined as those substances that, even in small quantities, can ignite within five minutes of contact with air. A pyrophoric gas is a chemical in a gaseous state that will ignite spontaneously in air at a temperature of 130° Fahrenheit (54.4° Celsius) or below.

Moisture in the air often increases the probability of the spontaneous ignition of pyrophoric materials.

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