Oxygen Flow Indicator Blinkers are visual devices used in aircraft to confirm the proper flow of oxygen to pilots and crew. These indicators feature a small chamber with a movable element, often a coloured disk or blinker, which oscillates or moves when oxygen flows through the system. Positioned near the oxygen regulator, they provide an immediate visual check, ensuring oxygen is being delivered properly. If the blinker stops moving, it signals a potential issue, such as a disconnected hose, malfunction, or depleted oxygen supply.

These devices became standard during World War II, particularly in high-altitude aircraft like the B-17 Flying Fortress and Spitfire, where oxygen systems were critical for preventing hypoxia during operations above 10,000 feet. As high-altitude and pressurised flights became common, blinkers ensured pilots could visually verify oxygen delivery at a glance. By the late 1940s, they were standard in both military and civilian aircraft, enhancing safety in aviation.