Installing a 36" range hood with an internal 3 speed 630 CFM 3 blower,damper and 6" vent pipe. Installation is in the area of an unused 10" square fireplace chimney flue.
Supposition: Will increase the hoods 6" vent to an 8" vent to increase air flow efficiency.
Option 1. Run vertical venting approximately 20 feet up chimney flue to top of chimney. A run of 8" galvanized pipe would be inserted into the 10" square chimney flue. The hood has a 6" vent and will require two 45 elbows connected together to enable tying to the 8" pipe in the chimney flue. A transition connector increasing the flow from 6" to 8" would also be required just after the elbows.
Option 2. Run venting horizontally approximately 3 feet through the chimney brick and out the chimney's exterior wall. A 90 elbow is required. Air flow could also be increased to 8" round.