A rotatable vent assembly system for areas where breathable airflow is required is disclosed herein. The rotatable vent assembly system improves airflow in any structure where breathable airflow may be a concern, including but not limited to air vacuum vaults, valve vaults, water tanks, pressure reducing valve units, or other confined structures. The rotatable vent assembly system helps reduce frost accumulation within riser pipes during winter months and improves breathable air within confined spaces. By reducing the accumulation of frost, the potential for pipe breakage is reduced, also reducing maintenance and replacement costs to municipalities and property owners for burst pipes. Rotating the vent control component at the top of a riser pipe connected to a pipe system controls the flow of breathable air by increasing or reducing airflow within the pipe system.