Before delivering, LP gases must be odorized with a warning agent down to a concentration in air of not over what fraction of the lower limit of flammability?

The correct answer is based on safety standards for handling liquefied petroleum (LP) gases. Before LP gases are delivered, they must be odorized to ensure that any leaks can be detected easily. This is crucial for preventing accidents and ensuring safety during storage and usage.

The requirement for odorization specifies that the warning agent's concentration must not exceed one-fifth (1/5) of the lower flammability limit (LFL) in air. This fraction was established to ensure that even at low concentrations, the odor can be detected by an average person. This level is considered an effective safety measure, as it allows people to notice the odor before the gas reaches flammable concentrations, thus providing an essential warning before a potentially dangerous situation arises.

Understanding this standard is important for anyone involved in the propane industry, as it highlights the critical balance between safety precautions and the operational characteristics of LP gases.