A Duct Integrity Test (DIT) is performed on the complete duct run between two chambers before OFC cable is blown. Compressed air is pumped into the duct and pressure is held for a specified duration to confirm there are no leaks, cracks, or faulty couplers in the section.
DIT results are recorded chamber-by-chamber and submitted to the highway authority as part of quality assurance documentation. Any failed sections are re-inspected, repaired, and re-tested before cable blowing commences.