A fire in a tunnel works like a chimney. It continuously pulls in oxygen, and the longer the tunnel, the stronger the suction. The fire spreads very quickly, and the tunnel fills with smoke and in no time. A mobile fire alarm and evacuation system for use in tunnel construction typically consists of radio smoke detectors and MOBS mobile evacuation units. It is optimized to handle high levels of dust and moisture inside the tunnel and thus to protect the construction workers and technology as well as to comply with the project plan.