The system allows workers to enter and exit small manhole size openings while maintaining continuous ventilation. Without such a device, duct fills the manhole openings, preventing rapid entry and exit. M.E.D. system is quick to assemble and the new swiveling elbow makes duct alignment easy. Requires RAMFAN UB20 to ventilate. Changing its cross-section from circular to elliptical and back to circular minimizes airflow velocity loss and optimizes airflow into a confined space, while providing adequate room for the worker to enter and exit unimpeded. The rugged plyethylene construction endures heavy negligent use and will last for years. Features Ventilate without blocking entry Maintain continuous airflow while working Included Manhole Entry Device 90° Elbow Universal Mount 20cm duct adapter for additional duct connections *RAMFAN UB20 SOLD SEPARATELY*