The Restriction Indicator measures inlet airflow at the Airsep unit. It shows red if the filter is dirty and engine air is restricted, which can lead to poor engine performance.
Once activated, it can be reset by pressing the top reset button. It attaches via a 1/8" NPT port near the base of the unit.
Restriction gauges are available rated for maximum vacuums of 15", 20" and 25" of water.
Except in unusual circumstances using the 15" gauge is recommended to avoid engine damage.