What alarm condition activates when the dew point of instrument air exceeds -22°F?

The instrument air alarm is activated when the dew point of instrument air exceeds -22°F because this indicates a potential issue with moisture levels in the air supply system. Instrument air is typically required to be dry, as moisture can damage sensitive equipment and affect the performance and accuracy of instruments that rely on this air for operation.

A dew point above -22°F signifies that the air is becoming more humid, which can lead to condensation within pneumatic systems. This can cause malfunctions, corrosion, or ice formation in the lines, ultimately compromising the integrity of the system and the operation of connected devices. Therefore, an alarm is essential to alert operators that the conditions are unfavorable, prompting them to take action to mitigate the risks associated with high humidity levels.

Other options such as humidity alert, temperature alert, and pressure alarm do not specifically address the dew point condition directly impacting instrument air quality and safety, placing more emphasis on different parameters that do not accurately represent the issue of moisture in the air supply.