DOT Hazard Class

Class 4.3

Dangerous When Wet

49 CFR §173.124(c)

Placard: Blue placard with flame symbol

ERG entries

118

Divisions

—

Packing groups

I · II · III

Compat groups

—

Definition

A material that, by contact with water, is liable to become spontaneously flammable or to give off flammable or toxic gas at a rate greater than 1 liter per kilogram of the material per hour.

Primary hazards

Produces flammable gases on contact with water
Gases may ignite spontaneously or be toxic
Fire will produce irritating, corrosive, and/or toxic gases
Contact with molten substance may cause severe burns

Public safety response

Isolate spill or leak area for at least 50 m (150 ft). Keep material dry. DO NOT USE WATER OR FOAM. Use dry sand, dry chemical (graphite, soda ash), or dry earth to smother.

Common materials in this class

Sodium, potassium, lithium, calcium carbide, alkali metal hydrides, metallic magnesium, zirconium hydride, aluminum phosphide.

UN1428Sodium UN1418Magnesium powder UN2813Water-reactive solid, n.o.s.UN1401Calcium UN2950Magnesium granules, coated

Packing groups

I: Reacts vigorously with water at ambient temperature — emits flammable gas that ignites spontaneously; or reacts readily with water at ambient temperature — flammable gas evolved at rate ≥ 10 L/kg/min
II: Reacts readily with water at ambient temperature — flammable gas evolved at rate ≥ 20 L/kg/hr
III: Reacts slowly with water at ambient temperature — flammable gas evolved at rate ≥ 1 L/kg/hr

Special provisions / notes

Some 4.3 materials also carry a 4.2 (self-heating) or 6.1 (toxic) subsidiary — check the shipping paper for all subsidiaries and use no-water extinguishing agents.

Definition

A material that, by contact with water, is liable to become spontaneously flammable or to give off flammable or toxic gas at a rate greater than 1 liter per kilogram of the material per hour.

Primary hazards

Produces flammable gases on contact with water
Gases may ignite spontaneously or be toxic
Fire will produce irritating, corrosive, and/or toxic gases
Contact with molten substance may cause severe burns

Public safety response

Isolate spill or leak area for at least 50 m (150 ft). Keep material dry. DO NOT USE WATER OR FOAM. Use dry sand, dry chemical (graphite, soda ash), or dry earth to smother.

Common materials in this class

Sodium, potassium, lithium, calcium carbide, alkali metal hydrides, metallic magnesium, zirconium hydride, aluminum phosphide.

UN1428Sodium UN1418Magnesium powder UN2813Water-reactive solid, n.o.s.UN1401Calcium UN2950Magnesium granules, coated

Packing groups

I: Reacts vigorously with water at ambient temperature — emits flammable gas that ignites spontaneously; or reacts readily with water at ambient temperature — flammable gas evolved at rate ≥ 10 L/kg/min
II: Reacts readily with water at ambient temperature — flammable gas evolved at rate ≥ 20 L/kg/hr
III: Reacts slowly with water at ambient temperature — flammable gas evolved at rate ≥ 1 L/kg/hr

Special provisions / notes

Some 4.3 materials also carry a 4.2 (self-heating) or 6.1 (toxic) subsidiary — check the shipping paper for all subsidiaries and use no-water extinguishing agents.