What is a formal inspection type that is irregular and unscheduled?

The choice of "Intermittent" as a formal inspection type that is irregular and unscheduled aligns with the definition of this inspection methodology. Intermittent inspections are characterized by their unpredictable timing and are often conducted as needed, rather than adhering to a set schedule or frequency. This type of inspection can be advantageous in identifying potential safety issues or compliance failures that may not be apparent during more regular inspections.

Periodic inspections, on the other hand, are typically carried out at scheduled intervals, which does not fit the criteria of being irregular. Focused inspections often target specific areas or concerns within a project and are usually planned, making them less random compared to intermittent inspections. General inspections, while broad in scope, are generally systematic in their approach over regular timeframes rather than being irregular. Hence, intermittent is correctly identified as the inspection type that is both irregular and unscheduled.