What is a key feature of post-indicator valves (PIV)?

Post-indicator valves (PIV) are specifically designed to be installed outside of a building, which is a key feature that allows firefighters and emergency personnel easy access to them during an emergency response. The external placement of PIV facilitates quick visibility and operation, enabling firefighters to control water flow to the sprinkler system or other fire suppression systems without needing to enter the building. This is crucial during emergency situations when time is of the essence and immediate access to such controls can significantly impact firefighting efforts.

The other choices reference features that either describe incorrect locations or functions not associated with post-indicator valves. For instance, PIVs are not located inside buildings, nor are they used to regulate smoke flow or designed to automatically shut off the water supply. Their primary purpose is to serve as a manual control point for water supply, which emphasizes the importance of their external placement.