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The tunnel ventilation system of Kolkata Metro's north-south corridor, also known as the Blue Line, is set to undergo a major upgrade. This underground stretch is the city's oldest and busiest metro route. The revamp will cover 15 underground stations between Belgachia and Rabindra Sarobar, most of which were built over 40 years ago.
Kolkata Metro's Ventilation System
Metro officials said the existing ventilation system was originally designed by IIT Kharagpur in the 1970s and later modified in 2011. While it has functioned well for decades, the system has now reached the end of its technical life. With the Metro fully shifting to air-conditioned trains, an upgrade has become essential. Metro Railway General Manager Subhransu Sekhar Mishra said the project will take about four to five years to complete and will cost around ₹585 crore. The contract has been awarded to the Indian arm of a Japanese company specialising in heating, ventilation, and air-conditioning systems. As part of the upgrade, powerful new ventilation fans will be installed, and the current water-based cooling system will be replaced with an air-based one. The project will also include heat-detection systems in tunnels to alert the control room during emergencies, improving passenger safety.
How is the New System Beneficial?
• The new system is expected to reduce energy use, save groundwater, improve cooling on platforms, and enhance fire safety in tunnels and stations.
• Officials explained that air-conditioned trains generate more heat while braking, making platforms warmer. The new fans will remove hot air efficiently and help maintain comfortable temperatures.
• These fans will consume less electricity and can operate for up to two hours at temperatures above 200°C.
• During a fire, they will help clear smoke and heat from tunnels. Each shaft between two stations will have three fans, including one standby unit.
• Additional exhaust fans will be placed above the tracks to remove hot air released by the trains' rooftop AC units, and this upgrade is expected to save about ₹21 crore annually in energy costs.
• The shift to air-cooled chillers will also save nearly 18 crore litres of groundwater every year, helping address falling water levels in parts of Kolkata.
