I have never owned an air purifier but it makes sense that if it's blowing toward the floor then definately you are going to be getting carpet fibers, dust, hair, or whatnot floating around the air. Just as a side question, do you vacuum before or after you dust? Always dust after you vacuum because vacuuming stirs up the debris (dust, dirt etc) and wait about a hour or two before you dust since that is how long it can take for the dust to settle after vacuuming (I used to sell expensive vacuums and I learned some valuable info hehehe).
As for it drying out the air, I have no idea but most air purifiers use negative energy. It traps allergens in the house and draws it in - purifying the air. And if you have an old dusty house, it only stands to reason that it might be drawing out the dirty moisteness of the air into the purifier. Sorry, I can't really help you with that one but excellent questions! I'm curious as to what others have to say.
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