Analyze an SDS

DOT Class 3: Flammable and Combustible Liquids

DOT Class 3 covers flammable liquids: liquids with a flash point of not more than 60 °C (140 °F), plus materials with a flash point at or above 37.8 °C (100 °F) that are intentionally heated and offered in bulk at or above their flash point. Combustible liquids, with flash points above 60 °C and below 93 °C (200 °F), are treated separately in the U.S. hazardous materials rules.

How it is defined

  • A flammable liquid for DOT purposes has a flash point of 60 °C (140 °F) or less (49 CFR 173.120). Some liquids are excepted under specific conditions, for example certain liquids with a flash point above 35 °C (95 °F) that do not sustain combustion in the prescribed test, so always check the regulation.
  • A flammable liquid with a flash point at or above 38 °C (100 °F) that does not meet the definition of any other hazard class may be reclassed as a combustible liquid for U.S. domestic transport; this option does not apply to vessel or air transport except where other means are impracticable (49 CFR 173.120(b)(2)).
  • A combustible liquid has a flash point above 60 °C (140 °F) and below 93 °C (200 °F). In the U.S., combustible liquids in non-bulk packaging are generally excepted from DOT hazmat requirements, but they are regulated in bulk packaging and they are still hazardous under OSHA, fire codes and workplace rules.
  • Class 3 liquids are assigned packing groups on the basis of initial boiling point and flash point.
  • Some Class 3 liquids have subsidiary hazards, such as toxicity (Division 6.1) or corrosivity (Class 8).

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 3. Combustible liquids in bulk use a red placard marked COMBUSTIBLE.

Packing groups

PG I: initial boiling point of 35 °C (95 °F) or less (great danger). PG II: flash point below 23 °C (73 °F) and initial boiling point above 35 °C (medium danger). PG III: flash point from 23 °C (73 °F) up to and including 60 °C (140 °F) (minor danger). How packing groups work.

Common examples

  • Gasoline (typically PG II)
  • Acetone, ethanol, isopropanol, toluene and many other solvents
  • Many paints, lacquers, adhesives and inks
  • Diethyl ether (PG I)
  • Diesel fuel, which is listed in Class 3 but, depending on its flash point, may be shipped domestically as a combustible liquid

How it relates to GHS

Corresponds to GHS flammable liquids Categories 1 to 4 (flame pictogram GHS02). The GHS categories use different cut-offs: Categories 1 and 2 have a flash point below 23 °C, Category 3 goes up to and including 60 °C, and Category 4 extends to 93 °C. DOT Class 3 generally covers GHS Categories 1 to 3, while Category 4 roughly corresponds to the combustible range.

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

  • Keep away from heat, sparks and open flames; use grounding and bonding when transferring.
  • Store in approved containers or flammable storage cabinets.
  • Ventilate to keep vapor below the lower explosive limit.

Where to find it on an SDS

Section 14 shows UN number (such as UN1203 for gasoline, UN1090 for acetone), proper shipping name, Class 3, packing group, and 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 flash point makes a liquid Class 3?

A liquid is a DOT Class 3 flammable liquid if its flash point is 60 °C (140 °F) or below, with some narrow exceptions. Liquids with flash points above 60 °C and below 93 °C (200 °F) are combustible liquids.

What are the Class 3 packing groups?

PG I has an initial boiling point of 35 °C or less, PG II has a flash point below 23 °C and a boiling point above 35 °C, and PG III has a flash point from 23 °C to 60 °C.

Is a combustible liquid regulated by DOT?

Generally only in bulk packaging in the U.S. Combustible liquids are still hazardous in the workplace and are regulated by OSHA and fire codes.

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