A giant, inflatable structure designed to prevent flooding in subways was rolled out, literally, for media observers inside a full-scale, mock subway tunnel. As the video shows, in under five minutes it is nearly filled with pressurized air—creating a flexible but extremely strong barrier. Full inflation is complete in less than 12 minutes. The live demonstration continued with the plug holding back simulated floodwater at 11.5 pounds per square inch pushing against it.