HazMat Tool — substance information

Potassium

HMT 15 June 2026

UN / ID: UN 2257
Hazard class: 4.3
Packing group: I
ERG guide: ERG 138
Special provisions: SP A7, SP A19, SP A20, SP B27, SP IB4, SP IP1, SP N6, SP N34, more…
Source: 49 CFR §172 (15 June 2026)

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Potassium

Potassium is a chemical element; it has symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives Wikipedia

Substance Data

Source: PubChem (HSDB, 05.12.2019)

CAS-Number

7440-09-7

Flash Point

n/a

Boiling Point

n/a

Emergency Response Guide No. 138

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

(3) Hazard Class

4.3
Dangerous when wet materials

(4) Identification number

UN 2257

(5) Packing Group

(6) Labels

Cargo Aircraft Only (Cargo Aircraft Only)

(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.

Steel packagings must be corrosion-resistant or have protection against corrosion.

Browse special provision A7

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

A20

Plastic bags as inner receptacles of combination packagings are not authorized for transportation by aircraft.

Browse special provision A20

B27

Tanks must have a service pressure of 1,034 kPa (150 psig). Tank car tanks must have a test pressure rating of 1,379 kPa (200 psig). Lading must be blanketed at all times with a dry inert gas at a pressure not to exceed 103 kPa (15 psig).

Browse special provision B27

IB4

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

Browse special provision IB4

IP1

IBCs must be packed in closed freight containers or a closed transport vehicle.

Browse special provision IP1

Battery fluid packaged with electric storage batteries, wet or dry, must conform to the packaging provisions of § 173.159 (g) or (h) of this subchapter.

Browse special provision N6

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

Minimum test pressure (bar)	4
Minimum shell thickness	6 mm
Pressure-relief requirements	Normal
Bottom opening requirements	Prohibited for liquids.

Browse special provision T9

TP7

The vapor space must be purged of air by nitrogen or other means.

Browse special provision TP7

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

(8) Packing Authorizations (§173.***)

(8A) Exceptions	151	see 49 CFR §173.151
(8B) Non-bulk	211	see 49 CFR §173.211
(8C) Bulk	244	see 49 CFR §173.244

(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

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 1382	Potassium sulfide, anhydrous or Potassium sulfide with less than 30 percent water of crystallization	4.2
UN 1847	Potassium sulfide, hydrated with not less than 30 percent water of crystallization	8
UN 1487	Potassium nitrate and sodium nitrite mixtures	5.1
UN 1420	Potassium, metal alloys, liquid	4.3
UN 3403	Potassium, metal alloys, solid	4.3
UN 2427	Potassium chlorate, aqueous solution	5.1
	Potassium dichloro isocyanurate or Potassium dichloro-s-triazinetrione, see Dichloroisocyanuric acid, dry or Dichloroisocyanuric acid salts etc
UN 1929	Potassium dithionite or Potassium hydrosulfite	4.2
UN 1422	Potassium sodium alloys, liquid	4.3
UN 3404	Potassium sodium alloys, solid	4.3
UN 3028	Batteries, dry, containing potassium hydroxide solid, electric storage	8
UN 3413	Potassium cyanide solution	6.1
UN 1680	Potassium cyanide, solid	6.1
UN 3422	Potassium fluoride solution	6.1
UN 1812	Potassium fluoride, solid	6.1