Product review (3 stars): Vents Only Through Left-Side Grease Filter
This review is for the Broan Allure QS2 range hood model (36" stainless) with a 300 CFM ventilator fan. The hood is installed in the ventless configuration. We've had the hood for quite a few years. From the beginning, the problem is that there is zero suction through the right-side (as you face the hood) filter. I'm a retired engineer, and I think the fault is in the design.

The single ventilator fan is located above the left-side filter and not centrally-located as it should be. When installing the fan for ventless operation, you are instructed to install a "ring" around the periphery of the ventilator fan's vanes. This ring (obstruction) will significantly reduce the ventilator fan's performance. In addition, for ventless operation you must install charcoal filters (left and right sides). The air-flow resistance of these filters, combined with the ventilator fan's reduced-performance and the off-center mounting of the fan result in absolutely zero suction through the right-side filter. That's a simple fact.

So, our expensive Broan range hood serves mainly as a good illumination source for our stovetop and provides some venting for the left-side stovetop elements. It does not provide any venting at all for the right-side stovetop elements (at least not through the right-side grease filter).

I don't know whether the range hood will perform adequately if installed in the vented configuration.

Update, February 16, 2013:  I just converted the range hood from re-circulation to ducted (7" round rigid galvanized steel duct). The duct path is 7 feet long and includes a 90-degree adjustable elbow and two adjustable offset sections (a 5/8" offset and a 2.5" offset are achieved by proper manipulation of 90-degree adjustable elbows). Venting is through a Broan wall-plate/damper mounted on a screened-porch wall (no in-line damper is used). The ducted range hood moves a lot of air, and the blower fan (though more powerful now) is considerably quieter. But, there is still no suction on the hood's right side. I suppose that the cooking volatiles from the right-side elements of the electric cooktop will meander to the left and find their way through the left-side grease filter and blower fan to the outside. The build quality of the hood is good, and it is easy to mount and hook up electrically. Its appearance is pleasing and the lighting is excellent. I just wish that the suction were more even across the width of the hood.

The following comment on the uneven suction is found in the installation manual for the Broan QP3 series range hoods:

"This hood utilizes an offset blower design to achieve greater
performance and lower sound levels. As a result, you may notice
that cooking impurities are more attracted to one side or appear
to be pulled-in faster than they appear on the opposite side. This
is completely normal. The hood has been designed and tested
to provide good capture of cooking impurities and odors under
all normal cooking conditions regardless of the cooking location
on the cooktop. Please note that cooking on the rear burners will
always result in the best capture of cooking impurities, regardless
of the hood design."