TunnelVentGuardian is a toolbox for planning and checking tunnel ventilation in both daily use and fire emergencies. The app shows how smoke layers, fans, and dampers behave, so engineers can see problems before a real event. Users can check when smoke may drop from the ceiling, when fans may stall, and how fan power changes with speed or damper angle. Simple loss checks help fine-tune pressure drop in the system, giving a clearer view of true fan demand. Jet and portal tools show how jet fans hug the roof and how fresh air or smoke gets drawn in or out at tunnel ends. The timing tool breaks down every delay from fire detection to alarms and fan commands, making response targets easier to meet. Multi-tunnel checks show how airflow in one tube can pull or push smoke in a neighbor through shared openings. Cost and wire-height tools round off the set, helping others balance long-term cost with safe clearances for vehicles and staff.