Which function does the automatic air vent serve?

• A. Removes air from the system
• B. Adds air to the system
• C. Removes water from the system
• D. Purges sediment from the system

Answer: (A)

An automatic air vent is used to release trapped air from a closed piping or hydronic heating system. Air can collect at high points and create air pockets that hinder water flow, cause noisy hammering, and reduce system efficiency. The vent automatically opens to let this air escape and then closes to stop water from leaking out. It isn’t meant to add air, remove water, or purge sediment—that’s handled by other components like air separators, purge valves, or sediment filters. By removing the air, the system circulates properly and operates more efficiently.