What type of dampers must be designed to maintain a safe opening at all times?

The correct answer is automatically opening dampers because these dampers are specifically designed to ensure that there is an open passage for airflow under certain conditions, often related to safety and ventilation. Their primary function is to respond to changes in the environment, such as detecting a rise in temperature due to fire, which prompts them to open automatically to allow for necessary ventilation or to prevent the buildup of harmful gases. This capability is crucial in maintaining safe internal conditions and ensuring that toxic fumes are exhausted appropriately.

In contrast, manually operated dampers require human intervention to open or close, which may not ensure a timely response in emergency situations. Remotely operated dampers, while they can be controlled from a distance, still rely on active handling, making them less reliable than automatic systems in urgent scenarios. Gravity dampers, on the other hand, can close under their own weight when airflow stops but do not have the active mechanism to open automatically; their design does not ensure an opening at all times unless airflow is present.

Thus, automatically opening dampers are essential for maintaining safety in environments where controlled ventilation is critical.