A 100 lb propane container must be transported so the pressure relief device communicates with what space of the container?

The pressure relief device of a propane container is designed to ensure the safety and integrity of the container during transport. It must communicate with the vapor space of the container. This is because, in a liquefied propane container, the liquid propane exerts pressure as it vaporizes. The vapor space is located above the liquid propane and serves as a reservoir for the vaporized gas.

By allowing the pressure relief device to communicate with this vapor space, any increase in temperature or pressure will trigger the relief device to release gas, thereby preventing the container from reaching dangerous pressures that could lead to a rupture or explosion. This design is critical for maintaining safety standards in the handling and transportation of liquefied petroleum gas.

The other options do not provide the necessary means for safe pressure regulation. The liquid space is beneath the vapor space and would not be effective for pressure relief. Air space typically refers to the outside environment, which is not relevant in this context. Lastly, the term "pressure space" is not used in standard industry terminology; therefore, it does not accurately describe the function of the pressure relief device in relation to the container's contents.