DOT Hazard Class

Class 2.2

Non-flammable, Non-toxic Gas

49 CFR §173.115(b)

Placard: Green placard with gas cylinder symbol

ERG entries

Divisions

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Packing groups

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Compat groups

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Definition

A non-flammable, non-toxic gas that is asphyxiant (dilutes or replaces oxygen in the atmosphere) or oxidizing (may generally cause or contribute to the combustion of other material more than air does).

Primary hazards

Simple asphyxiants in enclosed spaces
Cylinders exposed to fire may rupture violently and rocket
Contact with cryogenic liquids (e.g. liquid nitrogen) causes severe frostbite
Oxygen and other oxidizing gases accelerate combustion of other materials

Public safety response

Isolate spill or leak area for at least 100 m (330 ft) in all directions. Ensure adequate ventilation. Cool fire-exposed cylinders with unattended monitor nozzles.

Common materials in this class

Compressed air, argon, nitrogen, helium, carbon dioxide (including dry ice, UN1845), medical/industrial oxygen, refrigerant gases.

UN1002Air, compressed UN1006Argon, compressed UN1013Carbon dioxide UN1066Nitrogen, compressed UN1072Oxygen, compressed

Special provisions / notes

Oxygen and other oxidizing gases (e.g. UN1072, UN1073) carry the 5.1 subsidiary and require the OXYGEN placard when transported in bulk.