Chapter 4: Safe Handling of Flammable and Combustible Liquids

Revised January 2023

Flammable and Combustible Liquids

The International Fire Code and the National Fire Protection Association define flammable and combustible liquids according to their flash point, with flammable liquids having a flash point of less than 100 °F (38 °C) and combustible liquids having a flash point greater than 100 °F (38 °C). It should be pointed out, however, that the Globally Harmonized System for classifying and labeling chemicals that was recently incorporated into the OSHA Hazard Communication Standard defines all liquids with a flash point of less than 200 °F (93 °C) as flammable, with numerical hazard rating to indicate the specific hazard level (see Chapter 15).

Both flammable and combustible liquids are considered fire hazards. The following procedures should be implemented in order to reduce the fire risk associated with these materials.

  • Flammable chemicals should be used only in lab hoods (or other well ventilated areas) and away from sources of ignition. Similarly, combustible chemicals should not be used near ignition sources, and it is recommended that they be used in lab hoods whenever possible.
    • Flash point is directly dependent on the total (system) pressure with the flash point at reduced pressures being lower than at ambient pressure. Flash point values reported in the literature should be considered to be determined at ambient conditions unless specified otherwise.
  • Do not heat flammable chemicals with an open flame.
  • For highly flammable chemicals, static electricity or hot surfaces can serve as ignition sources.
    • Do not use electrical devices with cracked or frayed electrical wiring.
  • Transfer flammable liquids from containers of five gallon-capacity or less inside a laboratory hood (or other area with similar ventilation) to prevent accumulation of a flammable concentration of vapors.
  • Transfer flammable liquids from containers of greater than five gallon-capacity in a well- ventilated area outside the laboratory building, or in an approved flammable storage room.
  • When transferring flammable liquid from a bulk container (generally greater than five gallons), the containers must be electrically bonded and grounded.
  • Fire extinguishers appropriate for the fire hazards present must be available in all laboratories and storage areas.
  • Class D fire extinguishers must be available in the immediate work area when working with flammable metals such as magnesium, sodium, and potassium.
    • Contact the Fire and Life Safety section of Facilities Maintenance at (775) 784-8020 to inquire about Class D fire extinguishers.
    • When using only small quantities of flammable metals, dry soda lime or sand can be used to smother a fire; however, dry graphite must be used to extinguish lithium fires.

Storage of Flammable and Combustible Liquids

Guidelines for the safe storage of flammable and combustible liquids are contained in Chapter 16.

Chapter 5: Highly Reactive Chemicals