Mercaptan is a type of organic compound that contains sulfur. It is characterized by a strong, often unpleasant odor, similar to that of rotten eggs. Mercaptans are commonly used as odorants in natural gas, which is otherwise odorless, to help detect leaks. These compounds are also found in various natural sources, such as garlic and certain types of onions. In addition to their use in gas detection, mercaptans play a role in the production of chemicals and pharmaceuticals, making them important in both industrial and everyday applications.