UN 2257Potassium
Division 4.3
Dangerous when wet
Summary
UN 2257 is the UN number for potassium. It is classed in Division 4.3 (dangerous when wet) of Class 4 for transport. Packing group I. Emergency responders use ERG guide 138.
Emergency response
The Emergency Response Guidebook (ERG2024) guide for this number:
- Guide138Potassium
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 2257
- Name
- Potassium
- Hazard class
- Class 4: Flammable solids
- Division
- 4.3: Dangerous when wet
- Packing group
- I
- 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.
UN2257Potassium
Special provisions: A7, A19, A20, B27, IB4, IP1, N6, N34, T9, TP7, TP33, W31
- Class
- 4.3
- Packing group
- I
- 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.
Check the official sources
For emergency response, packaging and quantity limits, use these:
- CAMEO Chemicals: UN/NA 2257NOAA datasheets with the ERG response guide and isolation distances
- Emergency Response Guidebook (ERG)PHMSA's guide for first responders, free as a PDF or app
- 49 CFR 172.101 Hazardous Materials TableThe legal U.S. entry: proper shipping name, packing group, labels and special provisions