My air purifier is making more noise and the air output has decreased — what's wrong?

The filters are likely dirty, as high amounts of particles can block the pores in the filter and restrict airflow. Replace the filters — HEPA Filters should be replaced every year and the Pre-Filter and Enhanced Odor & VOC Filters every 3 months — and use only Certified Genuine Honeywell Filters to ensure proper performance. (Page 9)