An air purifier works hard every day, pulling dust, pollen, smoke and fine particles out of your room. That also means it collects a lot of dirt itself. When the filters and vents get clogged, the machine has to work harder, airflow weakens and the air may not be as clean as you think. Delhi and other northern cities see especially bad air in the winter months, so this is a good time to check your purifier. The steps below are for most home models, but always look at your manual first, since cleaning rules vary by brand and filter type.