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3543

UN 3543Articles containing a substance which in contact with water emits flammable gases, n.o.s.

Division 4.3

Dangerous when wet

Summary

UN 3543 is the UN number for articles containing a substance which in contact with water emits flammable gases, n.o.s. It is classed in Division 4.3 (dangerous when wet) of Class 4 for transport. Emergency responders use ERG guide 138.

Emergency response

The Emergency Response Guidebook (ERG2024) guide for this number:

  • Guide138Articles containing a substance which in contact with water emits flammable gases, n.o.s.

From the 2024 Emergency Response Guidebook (ERG2024), published by U.S. Department of Transportation, PHMSA. Read the full guide in the ERG or on CAMEO Chemicals.

Identification

UN number
UN 3543
Name
Articles containing a substance which in contact with water emits flammable gases, n.o.s.
Hazard class
Class 4: Flammable solids
Division
4.3: Dangerous when wet
What the class covers
Substances which, in contact with water, emit flammable gases.

U.S. Hazardous Materials Table

The entry for this number in 49 CFR 172.101.

  • UN3543Articles containing a substance which in contact with water emits flammable gases, n.o.s.

    • Technical name required in parentheses

    Special provisions: 131, 391

    Class
    4.3
    Packing group
    None
    Labels
    4.3

From the eCFR edition of 49 CFR 172.101 dated 2026-10-05 (section last amended 2026-09-08). The eCFR is an editorial compilation, not the official legal edition. Read the current table.

About Class 4

Class 4 covers flammable solids and other substances that can catch fire. Division 4.1 is flammable solids and self-reactive substances, 4.2 is substances that can spontaneously combust in air, and 4.3 is substances that give off flammable gas when wet.

See all Class 4 UN numbers

Check the official sources

For emergency response, packaging and quantity limits, use these: