The actuation device operating temperature of a ceiling radiation damper must be what above the normal temperature in the duct system?

The correct choice indicates that the actuation device for a ceiling radiation damper must be set to activate at 50 degrees Fahrenheit above the normal operating temperature in the duct system. This requirement is crucial for ensuring that the damper responds correctly to excessive temperatures, which can indicate a fire condition or other emergency situation.

Setting the actuation device to activate at this specific temperature above the normal duct temperature allows the system to effectively contain smoke and heat. It provides a safety mechanism that ensures the damper operates only when necessary, thus preventing the spread of fire and harmful gases through the ventilation system.

This temperature differential is an important aspect of fire safety compliance as specified in the relevant codes and standards, ensuring that the ventilation system functions properly during critical situations where containment of smoke and fire is essential.