What type of doors must be equipped with a device that ensures closing after being opened?

The correct answer is that self-closing doors must be equipped with a device that ensures they close automatically after being opened. Self-closing doors are typically installed in environments where it is crucial to maintain certain conditions, such as fire-rated doors that act as a barrier to smoke and flames. The self-closing mechanism can be a spring hinge or an automatic closer that activates when the door is released.

This feature is vital for safety and compliance with building codes, as it helps to prevent unauthorized entry, control temperature, and contain smoke and fire in case of an emergency. The requirement of a closing device on self-closing doors is significant for ensuring that they fulfill their protective roles effectively.

While the other types of doors mentioned may have their own mechanisms, they do not necessarily have the same requirement for an automatic closing feature after being opened. Manual closing doors rely on the user to close them, and automatic closing doors may operate differently in various contexts, but the specific requirement for self-closing functionality is uniquely relevant to the question asked.