Ventilation system (1) of a tunnel or covered road section (2), in which the tunnel (2) comprises at least a first tunnel tube or carriageway (11; 11, 12) with a first entrance (3; 3, 5) and a first exit (4; 4, 6) for traffic (T1; T1, T2) through the at least first tunnel tube (11), and the ventilation system (1) is equipped for: —the production of a blind flow or recirculation flow of air inside the at least first tunnel tube during use, and —the controlled discharge of air from the blind flow or recirculation flow at the entrance and/or exit of the at least first tunnel tube.