Why is mercaptan added to propane?

• A. To increase energy content
• B. To color the gas blue
• C. To improve combustion efficiency
• D. To provide a detectable odor so leaks can be smelled.

Answer: (D)

Propane and natural gas are odorless, so adding a mercaptan odorant gives a strong, distinctive smell even at very low concentrations. This makes leaks easy to detect before they become hazardous, allowing quick action to shut off the gas. The odorant is chosen because it stays in the gas and doesn’t significantly affect energy content or combustion, and it isn’t used to color the gas or improve burn efficiency.