A tunnel is like a complex organism that needs to “breathe” and function efficiently every day.
That’s why installation and finishing works are such an important stage of the project — they often remain invisible to passengers, yet they directly affect their comfort and safety. In recent weeks, we have made significant progress in two key areas: the ventilation plant and the sanitary rooms.
Powerful lungs of the tunnel
The tunnel ventilation system can be compared to lungs — it operates continuously, adapting to current conditions. It works in two main modes: everyday operation and fire mode. In everyday mode, its task is to ensure proper air quality for passengers on the stations and inside the tunnel. The system constantly monitors the levels of pollutants such as carbon monoxide (CO) and nitrogen oxides (NO), as well as visibility.
Interestingly, under normal conditions, a large part of the ventilation happens naturally. A tram entering the tunnel acts like a piston in a syringe — pushing air forward and drawing in fresh air behind it. This phenomenon, known as the piston effect, supports the entire system and improves its efficiency.
In emergency situations, the fire mode is activated — a system designed for special tasks. When smoke is detected, high‑power jet fans create a directional airflow that pushes smoke out of the tunnel and evacuation routes. This allows passengers to leave the danger zone safely and gives rescue teams better visibility and working conditions.
The numbers are impressive. The tunnel is equipped with 12 jet fans, each weighing around one ton — as much as a small car suspended from the ceiling. A single fan can move approximately 98,000 m³ of air per hour. The stations and tunnel are also equipped with an extensive network of ventilation ducts whose total length rivals the height of the tallest buildings. Additionally, the smoke‑extraction fans at Rondo Polsadu station can remove up to 32,000 m³ of smoke per hour.
The safety system operates automatically, responding to signals from fire detectors or commands from the control room. In case of danger, the affected zone is isolated by closing fire dampers. At the same time, overpressure is generated in stairwells and lift shafts to prevent smoke from entering evacuation routes. Smoke‑extraction fans are activated simultaneously to remove smoke from the endangered area.
The ventilation plant is therefore a key element of the tunnel infrastructure — the central hub for managing air and safety. All devices are continuously monitored, allowing quick detection of any faults and ensuring uninterrupted system operation.
A wide range of works
We have completed the main installation works in the ventilation plant. This is where the heart of the system responsible for air exchange in the tunnel is located. The installed air‑handling unit filters the air, heats or cools it, and provides supply and exhaust ventilation. Thanks to this, proper conditions can be maintained both in the tunnel and on the stations.
At the same time, we equipped the evacuation staircases with air‑supply units — crucial fire‑safety devices. In an emergency, they provide fresh air from outside and create overpressure that prevents smoke from entering evacuation routes. The system is complemented by fire dampers, which automatically close during a fire, limiting the spread of smoke and flames through the ventilation ducts. All of this is supported by extensive duct networks that transport air throughout the facility. In the coming weeks, we will connect the installations to power and begin initial start‑ups and testing.
Works also included the sanitary rooms. We have completed the main installation and finishing works there, including water and sewage systems. We prepared connections for washbasins, toilets and showers, and installed hot and cold water systems. Pressure tests confirmed that the system is leak‑free and functioning correctly. The next stage will be the so‑called “white assembly,” meaning the installation of visible fixtures and sanitary equipment.
