Metallic substance, water-reactive, self-heating, n.o.s
HMT 15 June 2026- UN / ID
- UN 3209
- Hazard class
- 4.3
- Packing group
- I (multiple — see tabs)
- ERG guide
- ERG 138
- Special provisions
- SP A7, SP W31
- Source
- 49 CFR §172 (15 June 2026)
Metallic substance, water-reactive, self-heating, n.o.s
A metal (from Ancient Greek μέταλλον (métallon) 'mine, quarry, metal') is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as opposed to nonmetallic materials which do not. Metals are typically ductile (can be drawn into a wire) and malleable (can be shaped via hammering or pressing). A metal may be a chemical element, such as iron, an alloy, such as stainless steel, or a molecular compound, such as polymeric sulfur nitride Wikipedia
| Emergency Response Guide No. 138 |
Hazardous Materials Table
Source: 49 CFR §172 (15 June 2026)(3) Hazard class4.3Dangerous when wet materials |
(4) Identification number |
(5) Packing Group |
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(6) Labels |
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(1) Symbols |
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| A7 | |
|---|---|
| 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 | |
|---|---|
| (10B) Other |
(3) Hazard class4.3Dangerous when wet materials |
(4) Identification number |
(5) Packing Group |
||||||||||||||
(6) Labels |
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(1) Symbols |
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| A7 | |
|---|---|
| IB5 | |
| IP2 | |
| T3 | |
| TP33 | |
| W31 | |
| W40 |
(8) Packing Authorizations (§173.***) 
| (8A) Exceptions | None | |
|---|---|---|
| (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 | |
|---|---|
| (10B) Other |
(3) Hazard class4.3Dangerous when wet materials |
(4) Identification number |
(5) Packing Group |
||||||||||||
(6) Labels |
||||||||||||||
(1) Symbols |
||||||||||||||
| A7 | |
|---|---|
| IB8 | |
| IP4 | |
| T1 | |
| TP33 | |
| W31 |
(8) Packing Authorizations (§173.***) 
| (8A) Exceptions | None | |
|---|---|---|
| (8B) Non-bulk | 213 | see 49 CFR §173.213 |
| (8C) Bulk | 242 | see 49 CFR §173.242 |
(9) Quantity Limits 
| (9A) Passenger aircraft/rail | 25 kg |
|---|---|
| (9B) Cargo aircraft only | 100 kg |
(10) Vessel stowage 
| (10A) Location | |
|---|---|
| (10B) Other |
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 | PG III | |
|---|---|---|---|
| 1 | G | G | G |
| 2 | Metallic substance, water-reactive, self-heating, n.o.s | Metallic substance, water-reactive, self-heating, n.o.s | Metallic substance, water-reactive, self-heating, n.o.s |
| 3 | 4.3 | 4.3 | 4.3 |
| 4 | UN 3209 | UN 3209 | UN 3209 |
| 5 | I | II | III |
| 6 | 4.3, 4.2 | 4.3, 4.2 | 4.3, 4.2 |
| 7 | A7, W31 | A7, IB5, IP2, T3, TP33, W31, W40 | A7, IB8, IP4, T1, TP33, W31 |
| 8A | None | None | None |
| 8B | 211 | 212 | 213 |
| 8C | 242 | 242 | 242 |
| 9A | Forbidden | 15 kg | 25 kg |
| 9B | 15 kg | 50 kg | 100 kg |
| 10A | E | E | E |
| 10B | 13, 40, 148 | 13, 40, 148 | 13, 40, 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. |