DOT Hazard Classes

The U.S. Department of Transportation sorts hazardous materials into nine classes, from Class 1 explosives to Class 9 miscellaneous materials. These match the UN classes used internationally. Five classes are split into divisions, giving the 2.1, 4.3 or 5.1 numbers you see on placards and in Section 14 of an SDS.

The class tells carriers and emergency responders the main hazard during shipping. It is separate from the GHS hazard classes used on workplace labels, although many materials carry both. For the identifier that goes with the class, see UN and NA numbers and packing groups.

Class 1: Explosives

Substances and articles designed to explode or that can detonate or burn very rapidly. Six divisions, 1.1 to 1.6.

Class 2: Gases

Compressed, liquefied, dissolved and refrigerated gases. Three divisions: flammable, non-flammable, poison.

Class 3: Flammable liquids

Liquids with a flash point of 60 °C (140 °F) or below, plus certain combustible liquids. Packing groups I to III.

Class 4: Flammable solids; spontaneous combustion; dangerous when wet

Flammable solids (4.1), spontaneously combustible materials (4.2) and materials dangerous when wet (4.3).

Class 5: Oxidizing substances and organic peroxides

Oxidizers (5.1) that promote combustion and organic peroxides (5.2) that are unstable and may burn or decompose violently.

Class 6: Toxic and infectious substances

Toxic substances (6.1) that can cause death or harm if swallowed, inhaled or absorbed, and infectious substances (6.2).

Class 7: Radioactive materials

Materials containing radionuclides above set activity concentrations. Labels are White-I, Yellow-II and Yellow-III.

Class 8: Corrosive materials

Liquids and solids that cause full-thickness destruction of skin or severely corrode steel or aluminum.

Class 9: Miscellaneous hazardous materials

Materials that present a hazard in transport but do not fit another class, such as lithium batteries and dry ice.

Classes and divisions at a glance

Class / division	Name	Label color and symbol
1	Explosives	Orange background, black symbol and numbers
1.1	Mass explosion hazard	Orange background, black symbol
1.2	Projection hazard	Orange background, black symbol
1.3	Fire hazard with minor blast or projection	Orange background, black symbol
1.4	Minor explosion hazard	Orange background, black numbers
1.5	Very insensitive substances	Orange background, black numbers
1.6	Extremely insensitive articles	Orange background, black numbers
2	Gases	Red (2.1), green (2.2), white (2.3)
2.1	Flammable gas	Red background, black or white flame
2.2	Non-flammable, non-poisonous gas	Green background, black or white cylinder
2.3	Poison gas	White background, black symbol
3	Flammable liquids	Red background, black or white flame
4	Flammable solids; spontaneous combustion; dangerous when wet	Red and white stripes (4.1), white over red (4.2), blue (4.3)
4.1	Flammable solid	White with seven vertical red stripes
4.2	Spontaneously combustible	White upper half, red lower half
4.3	Dangerous when wet	Blue background, white or black flame
5	Oxidizing substances and organic peroxides	Yellow (5.1), red over yellow (5.2)
5.1	Oxidizer	Yellow background, black flame over a circle
5.2	Organic peroxide	Upper half red, lower half yellow
6	Toxic and infectious substances	White background, black symbol
6.1	Toxic (poisonous) material	White background, black symbol
6.2	Infectious substance	White background, black symbol
7	Radioactive materials	Upper half yellow, lower half white
8	Corrosive materials	Upper half white, lower half black
9	Miscellaneous hazardous materials	White background, seven black vertical stripes in the upper half

Classes versus divisions

A class is the broad hazard type. A division splits some classes into sub-types with different behavior. For example, Class 2 gases are divided into flammable gas (2.1), non-flammable gas (2.2) and poison gas (2.3). A material can also have a subsidiary hazard, such as a flammable liquid that is also toxic, in which case it carries a label for each hazard.

Section 14 of the SDS is the first place to look. It lists the UN number, proper shipping name, hazard class and packing group. See SDS Section 14 and the glossary entry on DOT hazard classes.

Frequently asked questions

How many DOT hazard classes are there?

There are nine DOT hazard classes: 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids and related materials, 5 oxidizers and organic peroxides, 6 toxic and infectious substances, 7 radioactive materials, 8 corrosives and 9 miscellaneous hazardous materials. Classes 1, 2, 4, 5 and 6 are divided into divisions.

Where do I find the DOT hazard class on an SDS?

In Section 14, Transport information. It is listed with the UN number, proper shipping name and packing group.

Are DOT hazard classes the same as GHS hazard classes?

No. DOT classes describe the main hazard for transport and are shown on labels and placards. GHS classes describe hazards for workplace and consumer labels and are shown with pictograms and hazard statements. They overlap but are assigned under separate rules.

General reference only. Always follow 49 CFR and the shipper's current SDS. Page URL https://sdslookup.org/dot/hazard-classes/