As winter creeps in and the outside air gets colder, having a good air purifier for your living space (especially your bedroom) is essential to reducing airborne particles. Closed windows and older heating systems often trap stale air and indoor pollutants, and microscopic allergens like pet dander and dust mites circulate your home instead of wafting outside. Plus, heating devices like fireplaces, furnaces, and heaters can create soot, dust, and other potentially harmful odors.