What type of gas does a combination gas valve primarily control?

A combination gas valve is designed to control the flow of gas in heating systems, and it is adaptable to different types of gases, making it a versatile component in various heating applications. It can regulate natural gas, propane, and butane, thereby allowing for its use across multiple fuel types based on specific system requirements or customer preferences.

This adaptability is essential for ensuring that heating systems can operate efficiently and safely regardless of the gas source. Therefore, the correct answer encompasses all three types of gas—natural gas, propane, and butane—indicating the combination valve's multi-fuel capability. This flexibility is particularly advantageous in regions where different gases are available or preferred, ensuring comprehensive coverage in the options provided.