System Failure Indicator

Active systems must have a visual or audio system failure indicator, such as the one shown in Figure. 6-1.

Criteria for System Failure Indicators

1. Must provide a clear warning of system failure
   1. Visual or audible
2. Must be easily interpreted
   1. Example: U-Tube Manometer
3. Typically, active systems will have a manometer similar to the one shown in Figure. 6-1. A simple U-tube manometer is mounted to the system vent pipe. The manometer measures the operation of the system fan.
4. When the liquid levels in the legs of the manometer are uneven, a pressure differential exists, indicating correct operation of the fan and system.

Conversely, if the manometer liquid levels are even, the fan or system is not operating properly and needs repair

Manometer requirements:

• Indicates pressure or airflow
• Must be easily interpreted