HazMat Tool — substance information

Corrosive solids, flammable, n.o.s.

HMT May 2026

UN / ID: UN 2921
Hazard class: 8
Packing group: I (multiple — see tabs)
ERG guide: ERG 134
Special provisions: SP IB6, SP T6, SP TP33
Source: 49 CFR §172 (2026/05)

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Corrosive solids, flammable, n.o.s.

A corrosive material is a liquid or solid that causes full thickness destruction of human skin at the site of contact within a specified period of time. A liquid that has a severe corrosion rate on steel or aluminum based on the criteria in 49CFR 173.137(c)(2) is also a corrosive material. More Information

Emergency Response Guide No. 134

Hazardous Materials Table

Source: 49 CFR §172 (2026/05)

Packing group I
Packing group II

(3) Hazard Class

8
Corrosive liquids

(4) Identification number

UN 2921

(5) Packing Group

Comparison View of PG

(6) Labels

(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.

IB6

Authorized IBCs: Metal (11A, 11B, 11N, 21A, 21B, 21N, 31A, 31B and 31N); Rigid plastics (11H1, 11H2, 21H1, 21H2, 31H1 and 31H2); Composite (11HZ1, 11HZ2, 21HZ1, 21HZ2 and 31HZ1).
Additional Requirement: Composite IBCs 11HZ2 and 21HZ2 may not be used when the hazardous materials being transported may become liquid during transport.

Browse special provision IB6

Minimum test pressure (bar)	4
Minimum shell thickness	§ 178.274(d)(2)
Pressure-relief requirements	Normal
Bottom opening requirements	§ 178.275(d)(2)

Browse special provision T6

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

(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	1 kg
(9B) Cargo aircraft only	25 kg

(10) Vessel stowage

(10A) Location

Stowage category “B” means

(i) The material may be stowed “on deck” or “under deck” on a cargo vessel and 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; and
(ii) “On deck only” on passenger vessels in which the number of passengers specified in paragraph (k)(2)(i) of this section is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

12	see 49 CFR §176.84
25	see 49 CFR §176.84

Source: 49 CFR §176.84

(3) Hazard Class

8
Corrosive liquids

(4) Identification number

UN 2921

(5) Packing Group

Comparison View of PG

(6) Labels

(1) Symbols

(7) Special Provisions (§172.102)

IB8

Authorized IBCs: Metal (11A, 11B, 11N, 21A, 21B, 21N, 31A, 31B and 31N); Rigid plastics (11H1, 11H2, 21H1, 21H2, 31H1 and 31H2 ); Composite (11HZ1, 11HZ2, 21HZ1, 21HZ2 and 31HZ1); Fiberboard (11G); Wooden (11C, 11D and 11F); Flexible (13H1, 13H2, 13H3, 13H4, 13H5, 13L1, 13L2, 13L3, 13L4, 13M1 or 13M2).

Browse special provision IB8

IP2

When IBCs other than metal or rigid plastics IBCs are used, they must be offered for transportation in a closed freight container or a closed transport vehicle.

Browse special provision IP2

IP4

Flexible, fiberboard or wooden IBCs must be sift-proof and water-resistant or be fitted with a sift-proof and water-resistant liner.

Browse special provision IP4

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

Browse special provision TP33

(8) Packing Authorizations (§173.***)

(8A) Exceptions	154	see 49 CFR §173.154
(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

Stowage category “B” means

(i) The material may be stowed “on deck” or “under deck” on a cargo vessel and 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; and
(ii) “On deck only” on passenger vessels in which the number of passengers specified in paragraph (k)(2)(i) of this section is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

12	see 49 CFR §176.84
25	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	Corrosive solids, flammable, n.o.s.	Corrosive solids, flammable, n.o.s.
3	8	8
4	UN 2921	UN 2921
5	I	II
6	8, 4.1	8, 4.1
7	IB6, T6, TP33	IB8, IP2, IP4, T3, TP33
8A	None	154
8B	211	212
8C	242	242
9A	1 kg	15 kg
9B	25 kg	50 kg
10A	B	B
10B	12, 25	12, 25

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.

Note: In this segregation and separation chart are HazMat of hazard class 8 considered depending if there are liquid. Currently HazMat Tool is not able to to check if a HazMat is liquid or not. Therefore it is assumed as liquid. See 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 3516	Adsorbed gas, toxic, corrosive, n.o.s. Inhalation hazard zone A	2.3
UN 3516	Adsorbed gas, toxic, corrosive, n.o.s. Inhalation hazard zone B	2.3
UN 3516	Adsorbed gas, toxic, corrosive, n.o.s. Inhalation hazard zone C	2.3
UN 3516	Adsorbed gas, toxic, corrosive, n.o.s. Inhalation hazard zone D	2.3
UN 3308	Liquefied gas, toxic, corrosive, n.o.s. Inhalation Hazard Zone C	2.3
UN 3308	Liquefied gas, toxic, corrosive, n.o.s. Inhalation Hazard Zone D	2.3
UN 3505	Chemical under pressure, flammable, corrosive, n.o.s	2.1
UN 2925	Flammable solids, corrosive, organic, n.o.s.	4.1
UN 2742	Chloroformates, toxic, corrosive, flammable, n.o.s	6.1
UN 3362	Chlorosilanes, toxic, corrosive, flammable, n.o.s	6.1
UN 2988	Chlorosilanes, water-reactive, flammable, corrosive, n.o.s	4.3
UN 3286	Flammable liquid, toxic, corrosive, n.o.s.	3
UN 3180	Flammable solid, corrosive, inorganic, n.o.s.	4.1
UN 2986	Chlorosilanes, corrosive, flammable, n.o.s	8
UN 2985	Chlorosilanes, flammable, corrosive, n.o.s	3