Which of the following types of facilities must maintain operations 24-hours a day?

A critical access hospital is designed to provide essential healthcare services to rural and underserved areas, and it is required to maintain operations 24 hours a day. This is crucial because they serve as a primary access point for emergency and acute care for patients in remote locations, ensuring that immediate medical services are available at all times. The constant availability of care is vital for patient safety and timely treatment in emergencies, particularly in rural settings where other healthcare options may be limited.

In contrast, the other types of facilities mentioned serve more specialized purposes or have operating hours that do not necessitate around-the-clock operations. For instance, ambulatory care centers and ambulatory surgical centers generally provide outpatient services during regular hours, while radiation therapy centers typically operate on a schedule that accommodates patient needs rather than requiring 24-hour availability. Hence, only critical access hospitals are designated to operate continuously to align with their role in the healthcare system.