With the beginning of any new project, it is easy to get carried away in the lime-lite of a new idea and sail off into the sunset of potential possibilities. I like to take a grounded approach and start off with physical mockups to see if my idea is actually possible in 3D space. I placed the fan around my lab bench and got a good feel of the size, weight and volume of it. Is it too big? Is it too heavy to move? Is it cumbersome? The physical use and interaction between a user and a product are sometimes the most important aspect of the product, not just its intended purpose. Yes, cardboard boxes work great for props!In this case, I found the IBM server fan to be perfect for a fume extraction application not just because of the excellent EBM Papst fan, but also because of the glorious integration of a cartridge-like design. The fan features a fully enclosed sheet metal shell with integrated edge rail shelf, allowing for a tongue-and-groove like fit for potential add-ons, like, say a filter. A cleverly designed filter tray could take advantage of this joint and sit snugly on top of the fan yet below the shoulder, with nearly zero play. The overall size also felt right. The fan enclosure stands slightly taller than a water bottle and about the same in width and 4 inches in depth. Of course, I was after a happy medium. I wanted to keep the extractor to as small of a footprint as possible yet retain an easy level of assembly and practicality.
With these critical first questions answered, it was time to do some research. This involves spending a lot of time looking through product photos and searching for teardowns or broken items on ebay so I can find more details or perspectives on a device. After a bit of research, I found that yes, centrifugal fans were ideal for fume extraction because of the higher level of static pressure created by transforming the air than a traditional axial fan. Through some ebay searching, it turns out the high end fume extractors all use varying forms of centrifugal fans. After sifting through product pages, I found that the specifications of Hakko and Pace units closely matched the centrifugal fan found in the IBM server fan. Here is an image taken from an ebay lising that closely shows the Hakko fan and Pace fan.