The vertical pipes connecting the system main line(s) with the branch lines on the various levels of the facility are called ______.

• A. Vent Lines
• B. Risers
• C. Branch (lateral) lines
• D. Main lines

Answer: (B)

Vertical pipes that move gas from the building’s main supply to the branch lines on each floor are called risers. In hospital gas systems, main lines run through the building and carry the supply, while risers take that supply upward (or downward) to feed the branch lines on each level, which then deliver gas to the outlets. This differentiates risers from branch lines (the pipes on a given level that connect to individual outlets) and from vent lines (which serve venting or relief rather than supplying gas). Main lines are the larger distribution paths that feed the risers.