Office Of Environmental Health & Safety

Northeastern University
360 Huntington Avenue
170 Cullinane Hall
Boston, MA 02115-5000

phone: 617.373.2769
fax: 617.373.7622

ehs@neu.edu Image 2

Flammable and Combustible Liquid Definitions

Flammable Liquids

Defined as liquids having closed cup flash points below 100°F (37°C) and vapor pressures not exceeding 40 psi (276 kPa) (2.76 bar) at 100°F (37°C). Flammable liquids are referred to as Class 1 liquids.

  1. Class IA liquids - flash points below 73°F (22.8°C) and boiling points below 100°F (37.8°C).
  2. Class IB liquids - flash points below 73°F (22.8°C) and boiling points at or above 100°F (37.8°C).
  3. Class IC liquids - flash points at or above 73°F (22.8°C) and below 100°F (37.8°C).

Combustible Liquids

Defined as liquids having closed cup flash points at or above 100°F (37°C). Combustible liquids are referred to as Class II or Class III liquids.

  1. Class II liquids - flash points at or above 100°F (37.8°C) and below 140°F (60°C).
  2. Class IIIA liquids - flash points at or above 140°F (60°C) and below 200°F (93.4°C). c.
  3. Class IIIB liquids - flash points at or above 200°F (93.4°C).