Liquids with flashpoint below 73 °F (22.8 °C) and having a boiling point below 100 °F (37.8 °C) are classified as:

• A. Class IA
• B. Class IB
• C. Class IC
• D. Class II

Answer: (A)

Flammable-liquid classifications use two temperature measurements to gauge ignition risk: flashpoint and boiling point. When a liquid has a flashpoint below 23°C (73°F) and a boiling point below 37.8°C (100°F), it is placed in Class IA. This combination means the liquid can produce ignitable vapors at very low temperatures and will readily vaporize into a flammable atmosphere, creating a high fire risk even at room temperature. Because of that, the controls for handling and storage are the most stringent among the flammable-liquid categories. An example is diethyl ether, which has both a very low flashpoint and a low boiling point, placing it in Class IA.