Hazmat UN Number Lookup

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🏷️ Primary Hazard Class Filter

UN1923

Calcium dithionite or Calcium hydrosulfite

Spontaneously Combustible

Class 4.2PG II

CAS RegistryN/A

Hazchem / EAC1Y

ERG Guide Number133

49 CFR Placards & Labels

Spontaneously CombustibleClass 4.2

⇩ 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)

4.2

PIH Zone

—

Packaging references (49 CFR §173.xxx)

Exceptions (col 8A)

None

Non-Bulk (col 8B)

§173.212

Bulk (col 8C)

§173.241

Aircraft quantity limits (col 9)

Passenger / Rail (9A)

15 kg

Cargo Aircraft Only (9B)

50 kg

Vessel stowage (col 10)

Location (10A)

Other codes (10B)

Special provisions (col 7 — §172.102)

A19 A20 IB6 IP2 T3 TP33 W31

Hazard Classification & Risks

Class 4.2 — Spontaneously combustible; pyrophoric (ignites within 5 minutes of air contact) or self-heating (49 CFR §173.124). Packing Group II — medium danger.

Transport Regulations

Hazard class 4.2, Packing Group II. Placard/label codes: 4.2. Special provisions: A19, A20, IB6, IP2, T3, TP33, W31. Packaging (49 CFR §173): exceptions §None, non-bulk §212, bulk §241. Quantity limits: passenger aircraft/rail 15 kg, cargo aircraft only 50 kg. Vessel stowage: E (other: 13). 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.