Agreed, from what I've read, the sub 1-micron is the worst for you health-wise, and as mentioned here, invisible to the naked eye. The more filtration/air changes, the better. May be worth looking into grabbing a Dylos or equivalent air quality monitor to make sure whatever measures you're putting in place are actually working the way you think they are. I believe mine measures down to 0.3um?....a couple hundred bucks invested in having healthy lungs in the future is a bargain in my world. Also a big fan of cyclone + venting the DC outside but I understand that isn't always possible.