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

Nitrogen trioxide

HMT 15 June 2026
Reference only — HMT snapshot for inspection and audit support; not a shipping paper, placard mandate, or CVI record. Use Print / PDF below for field notes.
UN / ID
UN 2421
Hazard class
2.3
Packing group
ERG guide
ERG 124
Special provisions
SP 1
Source
49 CFR §172 (15 June 2026)

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Nitrogen trioxide


Nitrogen trioxide or nitrate radical is an oxide of nitrogen with formula NO3, consisting of three oxygen atoms covalently bound to a nitrogen atom. This highly unstable blue compound has not been isolated in pure form, but can be generated and observed as a short-lived component of gas, liquid, or solid systems. Like nitrogen dioxide NO2, it is a radical (a molecule with an unpaired valence electron), which makes it paramagnetic. It is the uncharged counterpart of the nitrate anion NO−3 and an isomer of the peroxynitrite radical OONO Wikipedia

Emergency Response Guide No. 124

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

(3) Hazard class

2.3
Poisonous gas

(4) Identification number Help

UN 2421

(5) Packing Group Help

(6) Labels Help

Poisonous gas (2.3) Oxidizers (5.1) Corrosive liquids (8)

(7) Special Provisions (§172.102) Help

×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.
1

(8) Packing Authorizations (§173.***) Help

(8A) ExceptionsNone
(8B) Non-bulk336see 49 CFR §173.336
(8C) Bulk245see 49 CFR §173.245

(9) Quantity Limits Help

(9A) Passenger aircraft/railForbidden
(9B) Cargo aircraft onlyForbidden

(10) Vessel stowage Help

(10A) Location
(10B) Other

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.

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