What defines the flash point of a liquid?

The flash point of a liquid is defined as the minimum temperature at which its vapor can form an ignitable mixture with air. This means that at or above this temperature, sufficient vapors are present to support combustion if an ignition source is introduced. Understanding the flash point is essential for safe handling and storage of flammable liquids in various environments, particularly in construction, where the presence of ignition sources is common.

The other options describe related concepts but do not accurately define flash point. For instance, the temperature at which a liquid ignites refers to the ignition point, which is typically higher than the flash point. The safe storage temperature indicates conditions to prevent potential hazards but does not capture the essence of vapor formation for ignition. Similarly, the temperature at which a liquid begins to evaporate relates to evaporation rate and volatility, not specifically to its flammability or the conditions for combustion. Thus, the defining characteristic of flash point is specifically its relation to the formation of ignitable mixtures with air at a determined temperature.