There are lots and lots of personal air purifiers for sale out there. So, make a great buying decision by using a little knowledge.
Old doors and frames painted before 1980 usually have lead-based paint. When the door rubs against the frame this will create dust. This area is called a friction point and can be found on windows as well. Lead dust is dangerous to children under 7.
The building next door is being remodeled and your living areas are full of construction dust.