Associate Safety Professional Practice Exam

What does the lower flammable limit represent?

1. Maximum vapor concentration supporting combustion

2. Minimum vapor concentration supporting combustion

3. Exclusively applies to solids

4. It is the threshold for ignition

The correct answer is: Minimum vapor concentration supporting combustion

The lower flammable limit (LFL), also known as the lower explosive limit (LEL), indeed represents the minimum concentration of vapor in air that can support combustion. Below this concentration, the mixture is too "lean" to ignite; there is not enough fuel in the air to sustain a fire. Understanding this concept is crucial for safety in environments where flammable vapors may be present, as it helps to assess the risk of fire or explosion. Knowing the lower flammable limit allows safety professionals to implement appropriate controls, such as ventilation or the use of explosion-proof equipment, to prevent concentrations from falling below this limit, thereby enhancing workplace safety. The significance of the other options lies in how they highlight the nuances of flammability. For instance, the maximum vapor concentration is for the upper flammable limit, which indicates the point beyond which the mixture can no longer burn due to a lack of oxygen; therefore, it does not describe the lower flammable limit. Exclusivity to solids is irrelevant, as lower flammable limits primarily involve gases or vapors. Lastly, considering ignition thresholds can be misleading, as these limits refer specifically to concentrations in air rather than the broader concept of ignition itself.