Hazmat UN Number Lookup

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🏷️ Primary Hazard Class Filter

UN2257

Potassium

Dangerous When Wet

Class 4.3PG I

CAS RegistryN/A

Hazchem / EAC4W

ERG Guide Number138

49 CFR Placards & Labels

Dangerous When WetClass 4.3

⇩ SVG

Not listed as a Reportable Quantity (RQ) hazardous substance under §172.101 Appendix A.

Not listed as a Marine Pollutant under §172.101 Appendix B.

Regulatory Facts

Packing Group

Symbols (col 1)

—

Labels (col 6)

4.3

PIH Zone

—

Packaging references (49 CFR §173.xxx)

Exceptions (col 8A)

§173.151

Non-Bulk (col 8B)

§173.211

Bulk (col 8C)

§173.244

Aircraft quantity limits (col 9)

Passenger / Rail (9A)

Forbidden

Cargo Aircraft Only (9B)

15 kg

Vessel stowage (col 10)

Location (10A)

Other codes (10B)

13, 52, 148

Special provisions (col 7 — §172.102)

A7 A19 A20 B27 IB4 IP1 N6 N34 T9 TP7 TP33 W31

Hazard Classification & Risks

Class 4.3 — Dangerous when wet. Contact with water emits flammable or toxic gas (49 CFR §173.124). Packing Group I — great danger.

Transport Regulations

Hazard class 4.3, Packing Group I. Placard/label codes: 4.3. Special provisions: A7, A19, A20, B27, IB4, IP1, N6, N34, T9, TP7, TP33, W31. Packaging (49 CFR §173): exceptions §151, non-bulk §211, bulk §244. Quantity limits: passenger aircraft/rail Forbidden, cargo aircraft only 15 kg. Vessel stowage: D (other: 13, 52, 148). Classified per 49 CFR §172.101.

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Source & sourcing note

Regulatory data mirrors the U.S. 49 CFR §172.101 Hazardous Materials Table and companion columns (packaging, quantity limits, vessel stowage, special provisions) as published by the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA).

Emergency-response content is drawn from the 2024 Emergency Response Guidebook (ERG), a joint publication of PHMSA, Transport Canada, and Mexico’s SCT.

The U.S. edition of the ERG and all U.S. federal regulations are public-domain works under 17 U.S.C. §105. Descriptions on this page are plain-English paraphrases; for any compliance decision, consult the authoritative text on eCFR Title 49 and the ERG at PHMSA.dot.gov. “ERG™” is attributed to PHMSA / Transport Canada / SCT and used nominatively.