Originally Posted by
Allan Speers
There's also an internal filter, which you can't see. You don't change that nearly as often, so you can't just look at the frst stage filter to know what's up.
Plus, some folks use an electrostatic front filter, which is hard to judge visually.
And last, I'm considering putting true HEPA filters on mine, as a final stage, if there's enough air pressure to do so.
But I started another thread on this topic, and there are defiitely other (cheaper) ways to go about this.