In a balance type vapor recovery system, what happens to the vapors?

In a balance type vapor recovery system, the correct response is that the vapors return to the transport truck. This system effectively manages the emissions of vapors during the refueling process by utilizing the principle of vapor displacement. When fuel is dispensed from the transport truck into the underground storage tank, the vapors in the tank are pushed back into the transport truck, which helps prevent the release of harmful vapors into the atmosphere.

This process is crucial for compliance with environmental regulations and for minimizing air pollution. By returning vapors to the transport truck, the system ensures that any potentially harmful substances are contained rather than released, thereby protecting the environment and public health. This vapor recovery method is often employed in various refueling operations and is an effective means of controlling emissions directly at the source. Other options do not accurately represent the function and purpose of a balance type vapor recovery system.