Here is an interesting issue that happened recently. A customer was interested in data outlets in the floor of an open office plan building (cubes) and wanted these on the first floor. The first floor was slab-on-grade meaning conduits under or within the slab to support these outlets. What cable should be run in these conduits? The rest of the building required plenum cable.
Well, in this case (by a different contractor, ask me how I found this out some time) the contractor installed Plenum cable in the conduit. The conduit was schedule 40 plastic PVC pipe which is watertight. But, not matter how you try to stop it, water will get in there eventually. In this case the cabling system tested fine and ran well for nearly a year before problems popped up. Network links started going down. Testing these links proved that the cabling was now failing RL. Fluke test equipment pointed to water penetration inside the conduit. It actually was able to identify exactly how many feet into the run the water was located. Nothing could be done to fix this. The cable was ruined.
How was this repaired? All of the in slab cable had to be replaced with wet location cable. This is in the NEC if you know where to look.
Lessons learned: Follow the NEC and local codes. There is a conflict in the code regarding how this cable exits the conduit and is terminated, we can help with that. Plus, this adds cost to the design. Work with a contractor, us, who knows not only the fastest way to terminate cable but also which cable is appropriate for the job at hand. Make sure you get a system that stays relevant and useful for the long haul.