Hood should be 6'' minimum larger than stove and at least 22'' deep if you cook. If you don't cook, don't sweat it at all.

My go to hood is Vent-a-Hood for all of my high end kitchens. They are quiet, highly efficient, and different technology than any that you suggested above as far as the filtering.

Hello Sunitha, The length of the duct pipe depends on the suction power of the chimney. Usually it is not recommended to have it more than 10 feet. You may have the duct near the chimney after having a core-cutting hole made. Ensure that the external end of the duct is atleast 12 inches and sloped downward so that there is no issues with rain. Thanks, Nitin CORNERSTONE DESIGNS Bangalore.

Please Read, 1) Following are the photos of my Mumbai apartment (10th floor) kitchen. Water heater and water purifier were already (haphazardly) installed by my contractor before I came to occupy the apartment. Answer : u can shift the purifier above sink , inside the cabinet which will be made by carpenter. 2) We now have to install cabinets above the counter. ( you can ) no problem. 3) I want to get the PNG gas pipes installed to replace the existing cylinders. Answer : This work you can do after carpentry work. 4) When I saw other homes it appears I not only need pipes but some ghastly looking meters/ valves etc. Answer : meter will be hidden inside above cabinet toward right side and pipes will be inside the hob side counter will transfer through the balcony wall to meter again. 1) The gas pipes will come from the wall next to the balcony doors. The sink is just next to this wall. Will it be possible to install the pipes and meters below the cooking counter or is that not practical? - - Don't know what are all the practical considerations. Safety, access to meter to take readings, location of the sink? ). everything is possible.. 2) If under the counter installation is not practical, where should the pipes and other boxes/meters go? as mentioned above.. 3) Is there any practical solution to clean up the wall with water purifier and heater? (please note the kitchen has a 6" thick beam on the top of the wall above the counter, also 6" think pillars one in the corner and the other large one near the microwave as shown. Additionally it has a protrusion on the ceiling, probably this houses the drain for the apartment above me. ( for above apartment kitchen nahani trap chamber it is... )