Which device is used in conjunction with a tank fitting to remove air from a cast iron boiler?

The device that is specifically used to remove air from a cast iron boiler in conjunction with a tank fitting is the automatic air vent. This component is designed to automatically expel trapped air from the system, which is essential for maintaining efficient operation and preventing issues like air locks.

An automatic air vent works by utilizing a float mechanism that opens a valve to release air when it detects excessive air buildup in the system. This helps ensure that hot water flows freely through the piping and heating surfaces, maximizing heat transfer and preventing overheating or damage to the boiler.

In contrast, while boiler fittings and other options provide various functionalities in a heating system, they do not serve the specific purpose of air removal as effectively as the automatic air vent. The air scoop is also useful for gathering air into a single location where it can be vented, but it is not as effective for automatic operation. The backflow preventer serves a different function, protecting the water supply from contamination, but it does not assist with air removal. Thus, the automatic air vent is the most suited for this task.