What happens when an air filter for 3D printers is designed by engineers with a passion for function, a refusal to compromise and a desire to do without bad smells or fumes? You get the Nevermore, a design for a recirculating activated carbon filtration system to handle VOCs (volatile organic compounds) from 3D printing.
The Nevermore Micro (and larger Nevermore Max) was originally intended to complement the Voron 3D printer design, but has been made to be used with just about anything else. These filters use 3D-printable parts, and are designed to be easily filled (and refilled) using bulk activated carbon instead of some sort of proprietary prepackaged filter like most commercial offerings. The Voron project is all about a printer without compromise, and the Nevermore comes from the same design ethos.
A Nevermore filter sits inside the build chamber and works by recirculating air inside as it passes through the activated carbon. The idea is that by concentrating on dealing with the problem at the source within a relatively small build room, one doesn’t need a lot of airflow. A small recirculating air filter can do the job effectively, but for best results the build chamber should be as sealed as possible.
One interesting caveat is that it turns out that not all activated carbon is the same, and it is absolutely essential to use only acid-free, steam-activated (not acid-washed) carbon in a recirculating filter like the Nevermore. There are horrific photos of oxidized metal surfaces resulting from the use of acid residue carbon, some of which took only minutes to occur. Fortunately, there are references to reliable sources for the known stuff.
3D printing is known to result in chemical and particulate emissions. This varies considerably depending on both material and type of printer, but it’s enough of a problem to warrant attention. One deals with particulates with something like a HEPA filter, but VOCs require a carbon filter. This is where the Nevermore comes in. Activated carbon filters will wear out simply from exposure to the air, so if one is serious about cleaning up VOCs when printing, it’s definitely worth looking into bulk carbon with a design like the Nevermore.