Which type of tank system requires a listed emergency shut-off valve at each dispenser for safety?

Suction type pumping systems are designed to draw fuel from the tank to the dispenser using atmospheric pressure. The requirement for a listed emergency shut-off valve at each dispenser is particularly important in these systems, as it provides an essential safety feature that can quickly interrupt the flow of fuel in case of an emergency or a spill. This type of valve ensures that fuel delivery can be stopped promptly, minimizing the risk of dangerous situations.

The other options, while they pertain to different systems of fuel delivery, do not specifically require the installation of an emergency shut-off valve at each dispenser to the same extent as suction systems. Gravity systems rely on the gravitational pull to move the fuel, and while they have their own safety measures, they do not necessitate this specific type of valve at every dispenser. Pressurized systems use pumps to move fuel and may have different safety mechanisms in place. Decommissioned tanks are not actively in use and thus do not require operational safety features since they are no longer dispensing fuel. Therefore, the emphasis on safety within suction type systems highlights why the presence of emergency shut-off valves is a critical requirement in this context.