Berbel extractor hood has the best recirculating technology but currently only available in Germany and UK. In conventional hoods grease is absorbed in filters. Grease particles clog the pores of the filter, and hood performance is reduced in increasing proportions. With the berbel principle grease is accelerated out of the air by centrifugal force, and is effectively separated at two points. The interior of the fan box remains virtually free of grease particles. There are no consequential costs, no unpleasant odors, no vermin, and there is no fire hazard. With berbel the unit can be cleaned with just one wipe, as easy as cleaning a Ceran hob. The stainless steel tray is made of the highest quality stainless steel and thus is dishwasher safe. http://www.berbel.de/int/index.php?id=300351 http://www.berbel.de/int/index.php?id=10

alas DH keeps asking why we can't have the microwave OTR, so I've looked into the Advantium. He says we can't do the 240, too hard to get a separate circuit, but I'll compromise and go with the 120. I was going to put the microwave in a cabinet, but that was when the cooktop was in an island. Now that I'm going with the GE Profile double oven freestanding range, it has to against the wall, so my whole design has to change. Just when I thought I had it all figured out, the puzzle pieces changed size and shape!

Rerouting the duct to the exterior is the better option to buying an inferior new hood! Recirculating is not a good option for indoor air quality.

I haven't searched for one, but it is possible that Broan/Best has a recirculating system with both grease filtering and charcoal-based odor filtering. To the question: Generally baffle filters are superior in grease extraction efficiency. This is why commercial hoods use baffles. Specifically, the baffles remove the larger end of the particle size spectrum while retaining their performance no matter how much grease is collected. The smaller end of the spectrum is expected to (hoped to) exit the system on the roof. The pressure loss of the baffles remains the same, greasy or not, and this allows the overall air flow to remain constant. However, baffles work by centrifugal extraction due to the air making two reversal in the baffle space. This requires some minimal velocity that likely depends on the details of the baffle design. For modest cooking where low blower speeds are adequate, there is a point where mesh filters -- if kept clean -- may become superior grease collectors. Mesh filters work by impingement. A hybrid baffle system seems to be intended to filter by mesh while providing the appearance of a baffle system. In some commercial applications, the stringent filtering requirements lead to stacked filters, the first usually being baffles, followed by mesh, ball bearing, and other schemes that address different parts of the particle spectrum. UV disassociation of grease and odor molecules is also popular.