Which statement is true regarding the operation of an HVAC pressure switch?

The statement that an HVAC pressure switch is a safety device to ensure proper airflow is accurate. Pressure switches are critical components in HVAC systems, as they monitor the pressure of air or refrigerant within the system to ensure that it operates safely and efficiently. If pressures fall outside of predetermined limits, the pressure switch can either shut down the system or prevent it from operating, thereby protecting the system from damage caused by issues like low refrigerant levels or airflow restrictions.

Additionally, this safety function is essential for preventing overheating or other failures that can lead to costly repairs, or even potentially hazardous situations. Proper airflow is vital for the efficiency and functionality of HVAC systems, making the pressure switch an indispensable element in maintaining system health and safety.

In contrast, the other statements do not accurately represent the function and versatility of pressure switches in HVAC systems. Some pressure switches may close rather than always remain open, and they can be utilized in both heating and cooling applications, further broadening their importance beyond just airflow management.