What concentration in air is the limit for odorizing LP gases prior to delivery?

The correct answer is that LP gases must be odorized to a concentration of at least 1/5 the lower limit of flammability prior to delivery. This standard operates on the principle of ensuring safety by making propane detectable to individuals in the event of a leak.

The lower limit of flammability (LLF) represents the minimum concentration of gas in air that can ignite and sustain combustion. By requiring the odorant (typically mercaptan) to be present at a level of 1/5 of this limit, any escaping gas can be quickly detected by the distinctive smell it imparts. This threshold is designed to provide a safety margin, allowing individuals to notice a gas leak before reaching a dangerous concentration. Consequently, ensuring proper odorization at this concentration level is crucial for enhancing detection and preventing potential accidents related to propane gas leaks.

Regarding the other concentration levels mentioned in the options, while they may not be officially designated for odorization requirements, they could either be too low (insufficient for effective detection) or potentially higher than necessary, which may not offer the level of safety deemed appropriate by regulatory standards.