How does NFPA 10 define flammable liquids of appreciable depth?

NFPA 10 defines flammable liquids of appreciable depth as having a depth greater than 1/4 inch. This specification is critical because it identifies the threshold at which liquids are considered to pose a significant fire hazard. When the depth exceeds this measurement, the potential for ignition and the intensity of a fire increase due to the greater surface area available for combustion. Understanding this definition helps in the proper selection and application of portable fire extinguishers, ensuring they are suitable for the specific risks associated with flammable liquids in that depth range.