What does the lower flammable limit represent?

The lower flammable limit (LFL) represents the minimum vapor concentration in the air that is required to support combustion. When the concentration of flammable vapors is at or above this level, a flame or other ignition source can ignite the vapor-air mixture. Below this concentration, the mixture is too lean to burn, meaning there aren't enough flammable vapors present to sustain combustion.

Understanding the LFL is crucial for safety practices, especially in industries where flammable substances are used or stored. It helps in assessing risks and implementing appropriate safety measures, such as ventilation and the avoidance of ignition sources in areas where flammable vapors may accumulate.

The other options do not accurately reflect the definition of the lower flammable limit. For instance, the maximum vapor concentration that can support combustion refers to the upper flammable limit, not the lower. The temperature at which ignition occurs pertains to the ignition temperature, and safe concentration levels for handling chemicals can vary widely depending on the specific chemical and its properties, rather than being defined by the flammable limits alone.