Number 2 is a vent for an exhaust fan like those found in bathrooms and laundry rooms.
Minimum gas appliance vent clearance from roof.
Stack vents may give off sewer gas so they should not be located within 3 feet of an operable window.
Each gas appliance must use a separate vent system.
3 chimney vent caps larger than 12 must be located at least 2 feet above the highest point and 2 feet higher than any portion of the building within a horizontal distance of 10 feet.
Appliances designed for natural draft venting and incorporating integral venting means shall be located so that a minimum clearance of 9 inches 229 mm is maintained between vent terminals and from any openings through which combustion products enter the building.
The minimum clearance to a perpendicular wall extending past the face of the fireplace is one inch 25 mm.
Common vent systems are prohibited.
Inspect the external vent cap on a regular basis to make sure that no debris is interfering with the air.
Venting systems vent connectors slope in ft upward to chimney vent not smaller than appliance flue up to 2 sizes larger than appliance flue length depends on type for single appliance single wall 75 of vent height b vent 100 of vent height 18 inch diameter for multiple appliances 34.