What is the UFL (Upper Flammable Limit)?

The Upper Flammable Limit (UFL) refers to the highest concentration of a flammable substance in the air that can support combustion. Beyond this concentration, the mixture becomes too rich in fuel for combustion to occur, which means there isn't enough oxygen to sustain the fire. Understanding the UFL is critical for safety in environments where flammable materials are handled or stored, as it helps in assessing the risk of fire or explosion in areas where these materials are present.

In practical terms, if the concentration of a flammable vapor exceeds the UFL, ignition will not occur because the mixture lacks sufficient oxygen for combustion. This concept is particularly important when managing and regulating environments where heating oil or similar materials are used, ensuring that safety measures are in place to maintain concentrations within safe limits.