When might the risk of fire or explosion from a fuel oil leak be considered small?

The situation where the risk of fire or explosion from a fuel oil leak is considered small typically occurs when the concentration of the fuel oil is at the lowest detectable level by smell. At this point, the amount of vapor present in the air is minimal, reducing the chances of forming an explosive mixture. Fuel oils generally need to be present at a certain concentration in the air to create an environment conducive to combustion. If the concentration is below the threshold where it can be easily detected by smell, it is also likely below the level that would pose a significant risk for ignition. This is crucial for safety as it indicates that the conditions are not conducive to a fire or explosion hazard at that concentration.

In contexts where fuel oil is involved, awareness of the specific concentration levels and their associated risks is essential for maintaining safety.