Partition off your modeling area.* Paint the walls. Be sure to clean the floor joyces overhead. A good exhaust system (paintbooth) vented to the outside will help keep the dust down. Keep your humidity as close to 50% as possible. Too dry and the air has static which breeds dust. Don't be afraid to clean your work area frequently, including vaccuming the floor.
Air purifiers are great though they don't solve the problem of dust...in fact they will stir it up as they circulate air over and around areas where the dust has settled. Like water, dust usually will win. It takes a lot of effort to keep it tame and away from your work space. The hobby by nature generates a ton of dust...sanding and painting are two major contributors.
*You can build walls or even use tarps or plastic...just as long as the area is sealed up.