DOT Hazard Class

Class 4.1

Flammable Solid

49 CFR §173.124(a)

Placard: Red-and-white vertical stripes with flame symbol

ERG entries

167

Divisions

—

Packing groups

II · III

Compat groups

—

Definition

A material, other than an explosive, that under conditions normally incident to transportation is liable to cause fire through friction, absorption of moisture, spontaneous chemical change, or retained heat from manufacturing/processing; or one that can be readily ignited and burns vigorously. Also includes self-reactive substances and desensitized explosives.

Primary hazards

Flammable — may be ignited by friction, heat, sparks, or flames
Some may burn rapidly with flare-burning effect
Powders, dusts, shavings may form explosive mixtures with air
Contact with water may release flammable, toxic, or corrosive gas

Public safety response

Isolate spill or leak area for at least 25 m (75 ft). Eliminate all ignition sources. Stay upwind. Do not spread dust — use gentle methods and containment.

Common materials in this class

Matches, sulfur, naphthalene, camphor, celluloid, magnesium powder, nitrocellulose (desensitized), metal powders.

UN1325Flammable solid, organic, n.o.s.UN1350Sulfur UN1944Matches, safety UN1408Ferrosilicon UN1330Matches, strike-anywhere

Packing groups

II: Medium danger
III: Minor danger

Special provisions / notes

Self-reactive substances (Types A-G) require temperature control if the SADT is ≤ 55 °C. Type A is prohibited from transport; Types B-F are permitted with specific packaging and control temperatures.

Definition

Primary hazards

Flammable — may be ignited by friction, heat, sparks, or flames
Some may burn rapidly with flare-burning effect
Powders, dusts, shavings may form explosive mixtures with air
Contact with water may release flammable, toxic, or corrosive gas

Public safety response

Isolate spill or leak area for at least 25 m (75 ft). Eliminate all ignition sources. Stay upwind. Do not spread dust — use gentle methods and containment.

Common materials in this class

Matches, sulfur, naphthalene, camphor, celluloid, magnesium powder, nitrocellulose (desensitized), metal powders.

UN1325Flammable solid, organic, n.o.s.UN1350Sulfur UN1944Matches, safety UN1408Ferrosilicon UN1330Matches, strike-anywhere

Packing groups

II: Medium danger
III: Minor danger