Analyze an SDS

DOT Division 2.1: Flammable Gas

Division 2.1 is the DOT hazard division for flammable gases: gases that can form an ignitable mixture with air at normal pressure, or that have a wide flammable range in air. Propane, butane, methane and hydrogen are typical examples.

How it is defined

  • In broad terms, a flammable gas is one that is ignitable when in a mixture with air at a concentration of 13 percent or less by volume, or that has a flammable range with air of at least 12 percentage points regardless of the lower limit.
  • Many flammable gases are heavier than air and can collect in low areas; hydrogen and methane are lighter than air.
  • Cylinders can fail violently in a fire.

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

Colors
Red background, black or white flame
Symbol
Flame

A red diamond label and placard with a flame and the number 2 at the bottom.

Packing groups

None. How packing groups work.

Common examples

  • Propane and butane (LPG)
  • Hydrogen
  • Methane and natural gas
  • Acetylene
  • Ethylene

How it relates to GHS

Corresponds to GHS flammable gases (flame pictogram GHS02). Aerosols with flammable contents are also classified under the GHS aerosol class.

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

  • Eliminate ignition sources, ground and bond where required.
  • Ventilate storage areas.
  • Use gas detection where leaks could accumulate.

Where to find it on an SDS

Section 14 shows Class 2, Division 2.1, a UN number such as UN1978 for propane, and an 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.

Frequently asked questions

What is a Division 2.1 gas?

A Division 2.1 gas is a DOT flammable gas. It can form an ignitable mixture with air and is shipped with a red flame label. Propane, hydrogen and acetylene are examples.

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