DOT Class 2: Gases

DOT Class 2 covers gases: materials that are gases at normal temperature and pressure, or that are shipped as compressed gases, liquefied gases, dissolved gases or refrigerated liquefied gases. It is split into three divisions: 2.1 flammable gas, 2.2 non-flammable, non-poisonous gas, and 2.3 poison gas.

How it is defined

• A gas is a material with a vapor pressure that makes it gaseous at ordinary temperature and pressure, or a material shipped in a pressurized container as a gas.
• Gases are divided by their primary hazard: flammability (2.1), no flammability or poison hazard (2.2) or toxicity (2.3).
• Some gases carry a subsidiary hazard, such as oxygen, which is a Division 2.2 gas with an oxidizing subsidiary hazard.
• Cryogenic or refrigerated liquefied gases such as liquid nitrogen are classified in Class 2, usually Division 2.2 unless flammable or toxic.
• The container itself is a hazard: pressurized cylinders can rupture or become projectiles if they are damaged or heated.

Summary of 49 CFR Parts 171 to 180. The regulations and the Hazardous Materials Table (49 CFR 172.101) control any shipment.

Label and placard

Each division has its own color and symbol; see the division pages. Cylinders also carry specification markings and test dates.

Packing groups

Class 2 does not use packing groups. Hazard is controlled by division, container specification and pressure. How packing groups work.

Common examples

• Propane, butane and hydrogen (2.1)
• Nitrogen, argon, carbon dioxide, oxygen and helium (2.2)
• Chlorine, ammonia (anhydrous), carbon monoxide (2.3)
• Aerosol cans, which are regulated through Class 2 provisions

How it relates to GHS

GHS classifies gases by physical hazard: flammable gases, gases under pressure (pictogram GHS04), oxidizing gases and aerosols. Toxic gases are classified under GHS acute toxicity by inhalation, and appear with the skull and crossbones pictogram.

• GHS: Flammable gases
• GHS: Gases under pressure
• GHS: Oxidizing gases
• GHS: Aerosols

DOT classes and GHS classes are assigned under different rules, so a product can have different severity labels in each. See also all GHS hazard classes.

Safe handling reminders

• Secure cylinders upright with caps on when not in use.
• Keep away from heat and ignition sources.
• Use the correct regulator and fittings; do not use a regulator on a different gas.
• Store flammable and oxidizing gases apart.

Where to find it on an SDS

Section 14 shows Class 2, the division, the UN number (such as UN1075 for liquefied petroleum gas) and often the ERG guide number. Look in Section 14: Transport information. Hazard classification for the workplace is in Section 2. You can also see how a UN number points to a response guide on the UN and NA numbers page.

Divisions in Class 2

Frequently asked questions

What are the three divisions of DOT Class 2?

Division 2.1 is flammable gas, Division 2.2 is non-flammable, non-poisonous gas and Division 2.3 is poison gas (toxic by inhalation).

Is oxygen a Class 2 material?

Yes. Oxygen is a Division 2.2 gas with an oxidizing subsidiary hazard, so it carries the green gas label and the yellow oxidizer label.

General reference only. It does not replace the supplier's SDS or the current federal regulations.