In what application would a sail switch be utilized?

A sail switch is specifically designed to detect airflow within a duct system, making it essential in applications where verifying that air is moving through the system is critical for operational safety and efficiency. When air flows, it moves a paddle or "sail" connected to the switch, which completes an electrical circuit and signals that airflow is present.

This device is typically used in HVAC systems to ensure that a furnace or boiler does not operate unless adequate airflow is detected, helping to prevent potential overheating and equipment damage. Proper airflow is crucial for efficient heating and cooling; if airflow is inadequate, it may indicate a blockage or failure in the system, necessitating quick action to remedy the situation.

In contrast, the other options focus on different aspects of environmental control: temperature regulation involves managing heat levels in a space, pressure sensing deals with detecting changes in gas or fluid pressure, and humidity control pertains to maintaining moisture levels in the air. None of these applications utilize a sail switch for their primary function, making airflow sensing the appropriate context for its use.