Answer;
-A vent stack
Explanation;
-A vent stack is best described by, the vertical, upper portion above the top-most fixture through which gases and odors escape the sanitary drainage system, carrying no liquids or solids.
-The vent stack usually runs parallel with the soil/waste stack and may either extend up through the roof or connect to a stack vent. While a stack vent is the uppermost portion of a soil/waste stack that continues the pipe from above the highest connected fixture out the roof.
