Breathe Naturally - January 2, 2024

Signs That Your Air Purifier Filter Needs Replacement


Key Takeways:

  • Increased noise when the unit is running indicates restricted airflow through a clogged filter.
  • Visible dirt and debris accumulation on the filter means it's no longer trapping particles efficiently.
  • Reduced airflow coming out of the vents signals that the filter is restricting air passage.
  • Lingering odors passing through the filter suggest it needs replacement.
  • Many experts recommend replacing filters every 3-6 months for optimal performance.
  • Check manufacturer instructions for the recommended replacement frequency.

Air purifier filters trap airborne particles like dust, pollen, pet dander, and smoke to improve indoor air quality. However, filters become less effective as they fill with contaminants. Replacing clogged, dirty filters maintains your air purifier's cleaning performance. Watch for these signs that indicate it's time to swap in a new air filter.

Increased Noise

As filters accumulate debris, airflow becomes restricted. This causes the fan to work harder to draw air through the clogged filter, which creates more noise. Listen for a louder hum or whooshing sound when your unit is running. This noise increase is a classic indicator that the filter needs changing due to excessive dirt buildup.


Visible Dirt and Debris

Check the condition of your filter by removing it and looking for a thick layer of dust, hair and other particles. If you see that the mesh material or pleated layers are covered in debris, the filter is no longer trapping contaminants efficiently. A filter blackened with accumulated dirt definitely requires replacement.

Reduced Airflow

Use an anemometer or measure airflow by holding a tissue near the purifier vents. Compare the air velocity to when you first installed the filter. Significantly reduced airflow indicates restriction from a clogged filter that needs changing. The filter may appear clean, but still restrict airflow if the mesh pores or pleats are filled with tiny particles.

Odors Passing Through

Filters are designed to remove airborne particles as well as trap odors and chemical pollutants. If you notice smells like cooking fumes, pet odors, or outdoor smoke getting through the filter, it's a sign that its absorptive capacity has reduced. Lingering odors indicate the filter material has saturated and needs to be replaced.


Manufacturer Recommended Interval

While the above signs help identify when your specific filter needs changing, manufacturers also provide general recommendations. Most experts advise replacing filters at least every 3-6 months. Check your owner's manual for the interval they suggest to maintain performance. Some high-end filters may last 9-12 months. Mark your calendar to remember when to swap filters.

When in doubt, earlier is better than later for filter changes. Clogged filters put strain on the motor and fail to fully purify your indoor air. Following the manufacturer's instructions and looking for these signs ensures your air purifier can operate at full filtration capacity. Keep replacement filters on hand so you can swap them in as soon as your current one shows signs of needing a change.


Environmental Protection Agency. "Indoor Air Filtration." Accessed November 20, 2023.

American Society of Heating, Refrigerating and Air-Conditioning Engineers. "Standard 52.2-2017." Accessed November 20, 2023