Hi calynn, We have an open air cooking spot. Maybe what you need is a low noise ventilation fan. Most fans have noise decibel rating at the back panel. , Here is a link that might be useful: Outdoor Kitchen Guide

@sarina: I have had the Kobe RA02 for about 8 months now. Being an engineer, I did the install myself, although the chimney cover is still not in place, as I need to redo the crown molding behind it (procrastination is the name of this game). Overall I like it, but that doesn't say much, as my previous ventilation was just a fan-in-a-ceiling-hole. The quiet setting is quiet, but the other two are noisy; without previous experience, the "sones" numbers don't translate well into actual noise levels. Otherwise, on High, the hood is pulling out all the smoke and airborne grease steaks in a cast-iron skillet produce. You will have to open a window or install a MUA to help it pull all that air volume. The baffles need scrubbing every month or so, but that's a very small price to pay for not having cabinetry and walls smeared in grease. The model you're looking at is a little more elaborate, as it has some sort of electronic control. The RA02 is bare-bones, just two rotary switches.

My mom has this problem too as well as drafts. In mine there are 2 mechanisms that kinda block it off - the obvious one on the outside of the house, and then just after the hood is ... I don't know how to describe it.. its essentially a one way valve. The hinge is in the center, so if any airflow is going its just like a thin line down the center of the pipe so barely restricts air flow and then when the air flow stops gravity + a very weak spring close the pipe off. I tried to find one for my mom but couldn't (didn't know where to look), mine came with the hood.

Ah. My apologies for abusive engineering descriptions. Sometimes I tend to unconsciously assume that all the previous stuff here has been read and digested, so all I have to do is present a reminder. Capture: The plume expands as it rises. The actual expansion angle is greater than 10 degrees outward, but ten degrees encompasses most of the higher velocity components for relevant cases. This means that the cone is wider the higher one measures above the pan base. At 36 inches hood height, for example, with a tangent of 10 degrees equal to 0.176, the plume has expanded outward by 36 inches times 0.176 or 6.4 inches. Similarly, for 30 inches, the plume has expanded by 30 times 0.176 = 5.3 inches. (Exactness is used here to clarify the calculation, not assert a defined boundary exists at the plume.) Suppose a pan base's maximum extent from the wall was 19 inches (which would be true of my induction cooktop if it were against a wall). Then one should aim for a hood aperture that was 19 + 6.375 = ~ 25 inches from the wall if 36 inches up. A 27-inch hood with lights in front of the aperture is close enough. Hence, your drawings have the angle going the wrong way. Imagine a really large traffic cone (without it weighted base). Slice it where it is the same diameter as the pan base and invert it over the pan. This inverted, truncated traffic cone, or rather a set of them perched on all the burners or hobs, can be imagined as defining the required boundary of the hood aperture. The desired hood aperture for good capture is independent of whether the structure of the hood is all metal or is metal inside of wood. Depending on your configuration, it may be best to space a smaller hood outwards and fill the gap at the wall side with some sheet metal. Side cabinets can help perform the function of side curtains in commercial configurations. (Note re pillog's comment. There is a small zone of high flow rate at the edges of the hood, and this has the effect of a slight increase in effective aperture.) Containment: Your analysis is correct. If the aperture is 6 sq. ft., then the desirable actual flow rate at full power is 90 x 6 = 540 cubic ft./min. Now where did I pull the magic number 90 from. Briefly, there are studies that have been published of plume velocities as a function of surface temperature, with induction and with gas. The gas cooking velocity (because the gas combustion products are entrained in the plume) causes more than a meter per second of plume rising velocity. The velocity with induction is typically less than a m/s. At the pan, the hood has NO effect on the velocity, and this essentially holds until the plume is close to the hood aperture. Another way to put it is that the hood captures the plume due to the plume's upward momentum (mass times velocity), which will not change until accelerated or decelerated by some force. When the plume reaches the baffles, it can intercept a gap and pass into the baffle space, or it can hit a metal part and potentially reflect. To keep the reflection in check, the air flow velocity of the hood has to be enough to change the reflection momentum to near zero and let the plume part be pulled into the baffles. When the air velocity is 90 ft/min average across the baffle space, it is about twice that at the baffle gaps, and this velocity is equal to that of the plume velocity. Also, I have observed this level working for the plume over my induction wok, and Greenheck suggests 85 ft/min for similar cooking (Figure 4, page 9 of the previous reference). So think of 90 ft/min as a suggestion that I don't think will prove to be too low. Too low of a hood velocity (CFM/sq. ft.), hence too low of a hood flow rate (below). Enough velocity (below) Blower specification: Yes, the factor of 1.5 is used to make up for the fact that blowers are specified by themselves (usually) hanging in free air, and what you have is a restrictive system that has to deal with baffle restriction, duct, and make-up air pressure losses. The relationship is given by the so-called "fan curve." For example, the Broan blower fan curve immediately below is just about done at well under an inch of water column pressure. Your requirements, depending particularly on baffles and MUA, may require a more "powerful" (higher nominal CFM) blower, as in the second figure. If the only loss were baffles, then the first figure would be barely good enough, because the baffles might have a pressure loss of about one or two tenths of an inch, w.c., at 90 CFM/sq. ft., depending on their aerodynamics. Throw in ducting and pressure losses in the MUA system (a whole giant topic of its own), and the tenths of inches build up leading variously to a need for one of the higher nominal flow rate models.Ekes out 540 CFM at a very low pressure drop (above) A blower with the 1.5 factor achieved (above). Keep in mind 1.5 is only a guess. A blower that would make up for many installation crimes (above), but which drives an unnecessarily more expensive MUA system to keep house pressure up. kas