I am having a new kitchen installed at the moment, and the fitter installed a new extractor hood.
It has an extraction rate of 550cubic.m/h
The outlet is 6" and supply with the hood is 150mm ducting.
My builders, due to ease of access have decided to use 4" ducting and a reducer.
They tell me this will not affect the extraction rate at all, however, I can't see how that can be.
Anyone knowledgeable about these things and can offer any advice, that would be appreciated.