DOT Hazard Class

Class 4.2

Spontaneously Combustible

49 CFR §173.124(b)

Placard: Red-bottom-half / white-top-half placard with flame symbol

ERG entries

Divisions

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Packing groups

I · II · III

Compat groups

—

Definition

A pyrophoric material (liquid or solid) that even in small quantities and without external ignition sources can ignite within 5 minutes of contact with air, OR a self-heating material that when in contact with air and without external energy supply is liable to self-heat.

Primary hazards

Some ignite spontaneously on exposure to air (pyrophoric)
Self-heat and may ignite when exposed to air or moisture
Fire produces irritating, corrosive, and/or toxic gases
Runoff may cause pollution and be highly reactive with water

Public safety response

Isolate spill or leak area for at least 25 m (75 ft). Keep material dry unless directed otherwise (some react with water). Do not touch. Cover with dry sand or other inert non-combustible.

Common materials in this class

White phosphorus, alkyl aluminums, alkyl lithiums, activated carbon, oily rags/fibers, pyrophoric metals (zirconium, hafnium, titanium powders).

UN1362Carbon, activated UN1373Fibers, animal or vegetable, oil-impregnated UN1383Pyrophoric metal, n.o.s.UN1932Zirconium scrap UN1381Phosphorus, white or yellow, dry

Packing groups

I: Pyrophoric — ignites within 5 minutes of exposure to air
II: Self-heating — heats spontaneously in contact with air but is not pyrophoric
III: Self-heating, lower hazard

Special provisions / notes

White phosphorus (UN1381) must be shipped submerged in water. Pyrophoric liquids fall under UN3194 and require inert-atmosphere packaging.

Definition

Primary hazards

Some ignite spontaneously on exposure to air (pyrophoric)
Self-heat and may ignite when exposed to air or moisture
Fire produces irritating, corrosive, and/or toxic gases
Runoff may cause pollution and be highly reactive with water

Public safety response

Isolate spill or leak area for at least 25 m (75 ft). Keep material dry unless directed otherwise (some react with water). Do not touch. Cover with dry sand or other inert non-combustible.

Common materials in this class

White phosphorus, alkyl aluminums, alkyl lithiums, activated carbon, oily rags/fibers, pyrophoric metals (zirconium, hafnium, titanium powders).

UN1362Carbon, activated UN1373Fibers, animal or vegetable, oil-impregnated UN1383Pyrophoric metal, n.o.s.UN1932Zirconium scrap UN1381Phosphorus, white or yellow, dry

Packing groups

I: Pyrophoric — ignites within 5 minutes of exposure to air
II: Self-heating — heats spontaneously in contact with air but is not pyrophoric
III: Self-heating, lower hazard

Special provisions / notes

White phosphorus (UN1381) must be shipped submerged in water. Pyrophoric liquids fall under UN3194 and require inert-atmosphere packaging.