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

Potassium hydrogendifluoride solution

HMT 15 June 2026

UN / ID: UN 3421
Hazard class: 8
Packing group: II (multiple — see tabs)
ERG guide: ERG 154
Special provisions: SP IB2, SP N3, SP N34, SP T7, SP TP2
Source: 49 CFR §172 (15 June 2026)

On this page

Potassium hydrogendifluoride solution

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

Emergency Response Guide No. 154

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

Packing group II
Packing group III

(3) Hazard class

8
Corrosive liquids

(4) Identification number

UN 3421

(5) Packing Group

Comparison View of PG

(6) Labels

(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.

IB2

_{Authorized IBCs:} Metal (31A, 31B and 31N); Rigid plastics (31H1 and 31H2); Composite (31HZ1).
_{Additional Requirement:} Only liquids with a vapor pressure less than or equal to 110 kPa at 50 °C (1.1 bar at 122 °F), or 130 kPa at 55 °C (1.3 bar at 131 °F) are authorized.

Browse special provision IB2

Glass inner packagings are permitted in combination or composite packagings only if the hazardous material is free from hydrofluoric acid.

Browse special provision N3

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	§ 178.274(d)(2)
Pressure-relief requirements	Normal
Bottom opening requirements	§ 178.275(d)(3)

Browse special provision T7

TP2

a. The maximum degree of filling must not exceed the degree of filling determined by the following:
TP2a

Where:
t_r is the maximum mean bulk temperature during transport,
t_f is the temperature in degrees celsius of the liquid during filling, and
α is the mean coefficient of cubical expansion of the liquid between the mean temperature of the liquid during filling (t_f) and the maximum mean bulk temperature during transportation (t_r) both in degrees celsius.
b. For liquids transported under ambient conditions α may be calculated using the formula:
TP2b

Where:
d₁₅ and d₅₀ are the densities (in units of mass per unit volume) of the liquid at 15 °C (59 °F) and 50 °C (122 °F), respectively.

Browse special provision TP2

(8) Packing Authorizations (§173.***)

(8A) Exceptions	154	see 49 CFR §173.154
(8B) Non-bulk	202	see 49 CFR §173.202
(8C) Bulk	243	see 49 CFR §173.243

(9) Quantity Limits

(9A) Passenger aircraft/rail	1 L
(9B) Cargo aircraft only	30 L

(10) Vessel stowage

(10A) Location

Stowage category “A” means the material may be stowed “on deck” or “under deck” on a cargo vessel or on a passenger vessel.

Source: 49 CFR §172.101(k)

(10B) Other

25	see 49 CFR §176.84
40	see 49 CFR §176.84
52	see 49 CFR §176.84
53	see 49 CFR §176.84
58	see 49 CFR §176.84

Source: 49 CFR §176.84

(3) Hazard class

8
Corrosive liquids

(4) Identification number

UN 3421

(5) Packing Group

III

Comparison View of PG

(6) Labels

(7) Special Provisions (§172.102)

IB3

_{Authorized IBCs:} Metal (31A, 31B and 31N); Rigid plastics (31H1 and 31H2); Composite (31HZ1 and 31HA2, 31HB2, 31HN2, 31HD2 and 31HH2).
_{Additional Requirement:} Only liquids with a vapor pressure less than or equal to 110 kPa at 50 °C (1.1 bar at 122 °F), or 130 kPa at 55 °C (1.3 bar at 131 °F) are authorized, except for UN2672 (also see special provision IP8 in Table 2 for UN2672).

Browse special provision IB3

Glass inner packagings are permitted in combination or composite packagings only if the hazardous material is free from hydrofluoric acid.

Browse special provision N3

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)	2.65
Minimum shell thickness	§ 178.274(d)(2)
Pressure-relief requirements	Normal
Bottom opening requirements	§ 178.275(d)(3)

Browse special provision T4

TP1

The maximum degree of filling must not exceed the degree of filling determined by the following:
TP1

Where:
t_r is the maximum mean bulk temperature during transport, and t_f is the temperature in degrees celsius of the liquid during filling.

Browse special provision TP1

(8) Packing Authorizations (§173.***)

(8A) Exceptions	154	see 49 CFR §173.154
(8B) Non-bulk	203	see 49 CFR §173.203
(8C) Bulk	241	see 49 CFR §173.241

(9) Quantity Limits

(9A) Passenger aircraft/rail	5 L
(9B) Cargo aircraft only	60 L

(10) Vessel stowage

(10A) Location

Stowage category “A” means the material may be stowed “on deck” or “under deck” on a cargo vessel or on a passenger vessel.

Source: 49 CFR §172.101(k)

(10B) Other

40	see 49 CFR §176.84
52	see 49 CFR §176.84
53	see 49 CFR §176.84
58	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 II	PG III
1
2	Potassium hydrogendifluoride solution	Potassium hydrogendifluoride solution
3	8	8
4	UN 3421	UN 3421
5	II	III
6	8, 6.1	8, 6.1
7	IB2, N3, N34, T7, TP2	IB3, N3, N34, T4, TP1
8A	154	154
8B	202	203
8C	243	241
9A	1 L	5 L
9B	30 L	60 L
10A	A	A
10B	25, 40, 52, 53, 58	40, 52, 53, 58

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.

Hinweis: In der Kompatibilitätstabelle sind Stoffe der Gefahrenklasse 8 nur dann zu berücksichtigen, wenn der Stoff flüssig ist. Derzeit kann HazMat Tool nicht prüfen, ob der Stoff flüssig ist. Dies wird daher hier angenommen. Siehe PHMSA Interpretation #09-0252.

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 3028	Batteries, dry, containing potassium hydroxide solid, electric storage	8
UN 1811	Potassium hydrogendifluoride solid	8
UN 1487	Potassium nitrate and sodium nitrite mixtures	5.1
UN 1499	Sodium nitrate and potassium nitrate mixtures	5.1
UN 1812	Potassium fluoride, solid	6.1
UN 2509	Potassium hydrogen sulfate	8
UN 1420	Potassium, metal alloys, liquid	4.3
UN 3403	Potassium, metal alloys, solid	4.3
	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 3422	Potassium fluoride solution	6.1
UN 1422	Potassium sodium alloys, liquid	4.3
UN 3404	Potassium sodium alloys, solid	4.3