Honeywell Pre-Filter for Air Purifier - Air purifier pre-filter features an advanced design to help capture larger airborne particles such as dust, lint, fibers, pet hair and fur from the air that passes through the filter. Activated carbon helps reduce common household odors to keep rooms smelling fresh. Easy-to-install design allows quick, simple replacement to ensure optimal performance. For the best performance, this air purifier filter should be replaced every three months.