dust control vent filters: Breathe easier and dust less often with these handy filters that fit easily into vents. Warm air from your furnace or cool air from your A/C will be filtered every time; will not affect air flow. Unscented polyester filters measure 4" x 10" and will last up to 12 weeks. Perfect for allergy sufferers! Controlling dust and pollen will also mean you'll be dusting less often!