A material's flash point is a metric of how easy it is to ignite the vapor of the material as it evaporates into the atmosphere. It is defined as the lowest material temperature required for fuel oils in the materials to begin to give off flammable vapors in the quantity high enough to support a flash of fire when ignited by an external source. A lower flash point indicates higher flammability. Materials with flash points below 100 °F (38 °C) are regulated in the United States by OSHA as potential workplace hazards.