What type of gase is heidelberg filled with?

Heidelberg is renowned for its picturesque scenery and historic architecture, but it is not specifically filled with any particular gas. However, like many urban areas, the atmosphere in Heidelberg consists primarily of nitrogen and oxygen, with trace amounts of other gases such as carbon dioxide and water vapor. If you're referring to a specific gas-related phenomenon or event in Heidelberg, please provide more context for a more accurate answer.