There have been a few posts on knifedogs about air filtration. I am sure there is someone here that can help you out. Speaking of out...that's where I would be headed if I attempted to do my knife making in the house. My wife would...(shudder). As it is, my garage (read shop) is very big and uninsulated. When the wind blows I can feel the air moving because of the vented soffits so I have not been overly concerned with air filtration. I am planning on either insulating the garage or building a shop in the near future, in which case I will be interested in an air filtration system.
I saw a post by our own boss dog where he incorporated the use of an electric box fan to draw dust and fumes out. This is probably the way I would be directed when I get there. Those box fans are cheap and effective at moving air. Filters range in price depending on what your intending to filter out and the size you want to use. I'm not sure about the type of filter you need. I dont know if a normal furnace filter would work or if you need something more job specific to do the trick.
My next concern is about heating and cooling in the shop in regards to air filtration. If I am heating or cooling my shop and then drawing the air outside for ventilation then I feel I am defeating the purpose of the heating and cooling. On the other hand, the air could be filtered and then reintroduced back into the shop I guess if after all it is being filtered.
Glad you posted, I was wondering what happened to you. Personally I have been battling the cold up here in the north. We got about 4 inches of snow last night and the temperature is well below the recommended temperature for one legged fat men to go out in it. I haven't completed a knife in a while but I have a bunch of "in process" stuff all over the bench.
Let us know how that makers mark and etching unit works out for you. I am interested to see what kind of results you get.
