The Limerick Tunnel was constructed as a result of a Public Private Partnership agreement between the National Roads Authority and Direct Route (Limerick) Ltd. Colt worked with Mott MacDonald Pettit and EVG Lufttechnik GmbH in providing Colt Labyrinth ventilators at each end of the tunnel. The Colt Labyrinth ventilators help prevent the build up of noxious gasses within the tunnel and create a steady flow of fresh air.
The length of a Labyrinth ventilator is practically unlimited, and in the Limerick tunnel each Labyrinth measured a huge 6.0m wide x 22.0m long. Each unit provides permanent weathered inlet ventilation for the tunnel at an acceptable louvre pressure drop.