A ventilation fan, 1966
Quebec Transport Ministry Archives
This fan could be reversed to pump out stale air from the tunnel. This feature was used in case of fire.
The Louis-Hippolyte Lafontaine Bridge–Tunnel The Louis-Hippolyte Lafontaine Bridge–Tunnel: A Feat of Engineering Between Two Shores Atelier d'histoire Mercier-Hochelaga-Maisonneuve