When abandoning a container underground, what should be used to remove remaining gas vapor?

Using a vapor connection to remove remaining gas vapor from an underground container is the correct approach because it is specifically designed for safely venting or extracting gas vapor in a controlled manner. This method helps to ensure that any residual propane gas is effectively managed while minimizing the risk of explosions or leaks, which can occur if vapors are not properly handled.

When employing a vapor connection, technicians can direct the gas to a safe area or appropriate recovery system, which adheres to safety regulations and standards for handling propane. This practice ensures both safety for the personnel involved and compliance with environmental guidelines.

Other methods like using an air compressor or a gas pump can be inappropriate or unsafe for this task. An air compressor might introduce air into the system, which could lead to a risk of combustion when mixed with propane. A gas pump is designed to move liquid fuel, not gas vapor, making it unsuitable for extracting vapor from a container. A vacuum attachment might not be effective for this purpose as it typically deals with solid or liquid materials rather than gases. Thus, the vapor connection is the most suitable and safe option for handling remaining gas vapors in abandoned underground propane containers.