HazMat Tool — substance information

Calcium dithionite or Calcium hydrosulfite

HMT 15 June 2026
Reference only — HMT snapshot for inspection and audit support; not a shipping paper, placard mandate, or CVI record. Use Print / PDF below for field notes.
UN / ID
UN 1923
Hazard class
4.2
Packing group
II
ERG guide
ERG 135
Special provisions
SP A19, SP A20, SP IB6, SP IP2, SP T3, SP TP33, SP W31
Source
49 CFR §172 (15 June 2026)

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Calcium dithionite or Calcium hydrosulfite


Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium Wikipedia

Emergency Response Guide No. 135

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

(3) Hazard Class

4.2
Spontaneously combustible materials

(4) Identification number Help

UN 1923

(5) Packing Group Help

II

(6) Labels Help

Spontaneously combustible materials (4.2)

(7) Special Provisions (§172.102) Help

×Note:
Special provisions may be very complex. The extracts are taken from 49 CFR §172.102. Please be careful with the information, as necessary, additional conditions may be applied that are not written here. Please check the original source and report bugs.
A19
A20
IB6
IP2
T3
TP33
W31

(8) Packing Authorizations (§173.***) Help

(8A) ExceptionsNone
(8B) Non-bulk212see 49 CFR §173.212
(8C) Bulk241see 49 CFR §173.241

(9) Quantity Limits Help

(9A) Passenger aircraft/rail15 kg
(9B) Cargo aircraft only50 kg

(10) Vessel stowage Help

(10A) Location
(10B) Other

Segregation chart for load, transport, and storage

This chart shows whether loading, transport, or storage with other hazard classes is permitted, prohibited, or restricted. Based on 49 CFR §177.848.

Prohibited Must not be loaded, transported, or stored together in the same vehicle or facility.
Permitted May be loaded, transported, or stored together.
Restricted May be loaded, transported, or stored together only with restrictions.