HazMat Tool — substance information Reference only — not a shipping paper, placard mandate, or CVI record.

Metal hydrides, water reactive, n.o.s

HMT 15 June 2026

UN / ID: UN 1409
Hazard class: 4.3
Packing group: I (multiple — see tabs)
ERG guide: ERG 138
Special provisions: SP A19, SP N34, SP N40, SP W31
Source: 49 CFR §172 (15 June 2026)

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Metal hydrides, water reactive, n.o.s

In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all compounds containing covalently bound H atoms. In this broad and potentially archaic sense, water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. In covalent compounds, it implies hydrogen is attached to a less electronegative element Wikipedia

Emergency Response Guide No. 138

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

Packing group I
Packing group II

(3) Hazard class

4.3
Dangerous when wet materials

(4) Identification number

UN 1409

(5) Packing Group

Comparison View of PG

(6) Labels

Cargo Aircraft Only (Cargo Aircraft Only)

(1) Symbols

This entry is signed with "G". The letter "G" identifies proper shipping names for which one or more technical names of the hazardous material must be entered in parentheses, in association with the basic description. (See §172.203(k)).

(7) Special Provisions (§172.102)

×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	Combination packagings consisting of outer fiber drums or plywood drums, with inner plastic packagings, are not authorized for transportation by aircraft. Browse special provision A19
N34	Aluminum construction materials are not authorized for any part of a packaging which is normally in contact with the hazardous material. Browse special provision N34
N40	This material is not authorized in the following packagings: a. A combination packaging consisting of a 4G fiberboard box with inner receptacles of glass or earthenware; b. A single packaging of a 4C2 sift-proof, natural wood box; or c. A composite packaging 6PG2 (glass, porcelain or stoneware receptacles within a fiberboard box). Browse special provision N40
W31	Non-bulk packagings must be hermetically sealed. Browse special provision W31

(8) Packing Authorizations (§173.***)

(8A) Exceptions	None
(8B) Non-bulk	211	see 49 CFR §173.211
(8C) Bulk	242	see 49 CFR §173.242

(9) Quantity Limits

(9A) Passenger aircraft/rail	Forbidden
(9B) Cargo aircraft only	15 kg

(10) Vessel stowage

(10A) Location

Stowage category “D” means the material must be stowed “on deck only” on a cargo vessel or on a passenger vessel carrying a number of passengers limited to not more than the larger of 25 passengers or one passenger per each 3 m of overall vessel length, but the material is prohibited on a passenger vessel in which the limiting number of passengers is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

13	see 49 CFR §176.84
52	see 49 CFR §176.84
148	see 49 CFR §176.84

Source: 49 CFR §176.84

(3) Hazard class

4.3
Dangerous when wet materials

(4) Identification number

UN 1409

(5) Packing Group

Comparison View of PG

(6) Labels

(1) Symbols

(7) Special Provisions (§172.102)

A19

Combination packagings consisting of outer fiber drums or plywood drums, with inner plastic packagings, are not authorized for transportation by aircraft.

Browse special provision A19

IB4

_{Authorized IBCs:} Metal (11A, 11B, 11N, 21A, 21B, 21N, 31A, 31B and 31N).

Browse special provision IB4

N34

Aluminum construction materials are not authorized for any part of a packaging which is normally in contact with the hazardous material.

Browse special provision N34

N40

This material is not authorized in the following packagings:
a. A combination packaging consisting of a 4G fiberboard box with inner receptacles of glass or earthenware;
b. A single packaging of a 4C2 sift-proof, natural wood box; or
c. A composite packaging 6PG2 (glass, porcelain or stoneware receptacles within a fiberboard box).

Browse special provision N40

Minimum test pressure (bar)	2.65
Minimum shell thickness	§ 178.274(d)(2)
Pressure-relief requirements	Normal
Bottom opening requirements	§ 178.275(d)(2)

Browse special provision T3

TP33

The portable tank instruction assigned for this substance applies for granular and powdered solids and for solids which are filled and discharged at temperatures above their melting point which are cooled and transported as a solid mass. Solid substances transported or offered for transport above their melting point are authorized for transportation in portable tanks conforming to the provisions of portable tank instruction T4 for solid substances of packing group III or T7 for solid substances of packing group II, unless a tank with more stringent requirements for minimum shell thickness, maximum allowable working pressure, pressure-relief devices or bottom outlets are assigned in which case the more stringent tank instruction and special provisions shall apply. Filling limits must be in accordance with portable tank special provision TP3. Solids meeting the definition of an elevated temperature material must be transported in accordance with the applicable requirements of this subchapter.

Browse special provision TP33

W31

Non-bulk packagings must be hermetically sealed.

Browse special provision W31

W40

Non-bulk bags are not allowed.

Browse special provision W40

(8) Packing Authorizations (§173.***)

(8A) Exceptions	151	see 49 CFR §173.151
(8B) Non-bulk	212	see 49 CFR §173.212
(8C) Bulk	242	see 49 CFR §173.242

(9) Quantity Limits

(9A) Passenger aircraft/rail	15 kg
(9B) Cargo aircraft only	50 kg

(10) Vessel stowage

(10A) Location

Source: 49 CFR §172.101(k)

(10B) Other

13	see 49 CFR §176.84
52	see 49 CFR §176.84
148	see 49 CFR §176.84

Source: 49 CFR §176.84

Packing group comparison

Multiple packing groups apply to this entry. See assignment criteria in 49 CFR §173 Subpart D. Details are in the tabs above; differences are highlighted.

	PG I	PG II
1	G	G
2	Metal hydrides, water reactive, n.o.s	Metal hydrides, water reactive, n.o.s
3	4.3	4.3
4	UN 1409	UN 1409
5	I	II
6	4.3	4.3
7	A19, N34, N40, W31	A19, IB4, N34, N40, T3, TP33, W31, W40
8A	None	151
8B	211	212
8C	242	242
9A	Forbidden	15 kg
9B	15 kg	50 kg
10A	D	D
10B	13, 52, 148	13, 52, 148

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.

Hazard class	8	7	6.1	5.2	5.1	4.3	4.2	4.1	3	2.3B	2.3A	2.2	2.1	1.6	1.5	1.4	1.3	1.1/1.2
1.1/1.2
1.3
1.4
1.5
1.6
2.1
2.2
2.3A
2.3B
3
4.1
4.2
4.3
5.1
5.2
6.1
7
8

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

Similar substances

UN / ID	Proper shipping name	Hazard class
UN 2698	Tetrahydrophthalic anhydrides with more than 0.05 percent of maleic anhydride	8
UN 3182	Metal hydrides, flammable, n.o.s	4.1