Pictogram 1: Flame - Self-Heating

Self-heating chemicals are classified under Pictogram 1, the Flame pictogram. A self-heating substance or mixture is a solid or liquid substance or mixture (other than a pyrophoric liquid or solid) that may self-heat when exposed to air. Self-heating substances or mixtures differ from a pyrophoric liquid or solid in that self-heating substances will ignite only when in large amounts (such as kilograms) and after long periods of contact time (such as hours or days) with air.

Self-heating is defined as "a process where the gradual reaction of that substance or mixture with oxygen in air generates heat. If the rate of heat production exceeds the rate of heat loss, then the temperature of the substance or mixture will rise which, after an induction time, may lead to self-ignition and combustion."

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