Conduit
CSI Division 26, Electrical
Rigid or flexible tubing that protects and routes electrical wiring through a building's walls, floors, and ceilings, sized specifically for the number and gauge of conductors it will carry, a code-governed calculation called conduit fill, not just whatever size happens to be on the truck.
Why it matters
Overfilling a conduit with more or larger wire than its fill rating allows makes it harder for heat generated by the conductors to dissipate, a code violation that can create a real fire risk hidden inside a wall long after the work is inspected and covered.
On a real project
An electrician calculates conduit fill for a run carrying several circuits, sizing the conduit to the code-required capacity rather than assuming a commonly used size will be sufficient, before pulling wire through it.
Who this matters most to
An Electrician selects and installs conduit sized correctly for its conductor load, a calculation that's easy to get wrong under schedule pressure. A Quality Control Manager spot-checks conduit fill on larger electrical rough-in scopes, since an overfilled conduit looks identical to a correctly filled one from the outside.
Where this goes wrong
An electrical crew pulls more circuits through an existing conduit run than its fill rating allows, reasoning that the conduit still has physical room for the wire. The overfill isn't caught during a routine visual inspection, since fill violations aren't visible without doing the calculation, and it isn't discovered until a later code review flags the as-built conditions.