Looking at your experience and the recommendations of our router forum buddies, I’d say you are or will be sitting pretty good with regard to wearable apparatus others recommend. What concerns me is what happens when you are still in your shop and not wearing your apparatus– especially since you are experiencing allergies. If you do a little digging, you can find others that are in your shoes and have some excellent experience and recommendations for the shop itself.
In a nutshell, wood dust comes in two unhealthy forms:
• the stuff you can see, and
• the stuff you can’t (which is actually worse).
IF your shop is relatively small and lucky enough, you might be able to beat both forms of dust with a HEPA shop vac, and cross-ventilation via an fan in an open window, a fan, and an opposite open door. If that’s not enough, you’ll need to find more mechanical approach to get both “stuffs” out of your shop.
Should you opt for a system involving filtration, each form of wood dust should be considered separately.
If you only use a coarse filter system, it will remove the stuff that you see floating in the air, but the smallest particles pass right through it. Worse yet, these original particles are joined by the next batch as you work, so the air quality deteriorates and you can’t even see it.
If you only use a filter system fine enough to capture the “no-see-ums”, they tend to clog, causing MUCH MAINTENANCE or system failure. At least you can see the failure, but cleaning up a whole shop can really cut into your work time and long-term health.
Personally, I really like twmv86’s ideas of using multiple box fans, but I might try varying the MERV ratings between 13 and 17 to capture a larger span of particle sizes. Further, I have a friend with an updraft furnace fan like twmv86 also described. His uses a hospital-grade HEPA filter and it all rests on a heavy metal cart. His works great because he also uses a dust cyclone AND filter setup. I’m so impressed that I’m working on one for my shop now! Bill Pentz has a cool design that uses a tall filter resting vertically on the floor with a vortex fan atop to pull and direct filtered air around the shop. Way Cool.
Lastly, PROPERLY SIZED dual filtration systems can work together, but you’ll likely need a particle counter to assure it’s working initially and then as a check periodically. These units can feel a bit pricey, but some woodworking and CNC groups buy a unit together that can be shared with its members.