India’s first underwater metro twin tunnel project in Kolkata, the East-West Metro, added another feather to its cap on Monday by getting India’s deepest metro ventilation shaft on the banks of the Hooghly River at 43.5m depth equalling 15-story building.

A ventilation shaft is crucial in underground Metro construction as it facilitates evacuation of passengers from the tunnel to ground level in case of any emergency situation.

The shaft is also used for air circulation, pumping air in and out of the air conditioning system, and ensure the flow of air in the tunnels to prevent passengers from feeling suffocated.

The ventilation shaft is also equipped to extract smoke in case if a fire breaks out. The metro ventilation shaft located on strand road is 43.5m deep having a diameter of 10.3m.

The Kolkata Metro Line 2 (Line 2 or East-West Corridor) is a rapid transit line of the Kolkata Metro that is eventually set to connect Teghoria with Howrah by going underneath the Hooghly River. In this process, Line 2 is set to be India's first underwater metro tunnel.