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HEPA Filters for Air Quality: A Beginner's Guide

June 18, 2026 · The Clime Team
HEPA Filters for Air Quality: A Beginner's Guide

High-Efficiency Particulate Air (HEPA) filters are essential components in maintaining clean indoor air. They are designed to capture a significant percentage of airborne particles, thereby enhancing air quality.

What Are HEPA Filters?

HEPA filters are mechanical air filters that remove at least 99.97% of particles as small as 0.3 microns in diameter. This includes dust, pollen, mold spores, bacteria, and any airborne particles with a size of 0.3 microns. The 0.3-micron size is considered the most penetrating particle size (MPPS), meaning it's the hardest size for filters to capture. Particles larger or smaller than 0.3 microns are trapped with even higher efficiency. (19january2021snapshot.epa.gov)

How Do HEPA Filters Work?

HEPA filters consist of a dense, pleated mat of fine fibers, typically made of glass or synthetic materials. As air passes through the filter, particles are captured through three primary mechanisms:

  • Interception: Particles following the airstream come within one radius of a fiber and stick to it.

  • Impaction: Larger particles cannot follow the airstream's curves around fibers and collide directly.

  • Diffusion: The smallest particles move erratically due to Brownian motion and collide with fibers at high rates.

These combined mechanisms allow HEPA filters to effectively capture a wide range of particle sizes. (cleanaircritic.com)

What Do HEPA Filters Remove?

HEPA filters are effective at capturing:

  • Dust

  • Pollen

  • Mold spores

  • Bacteria

  • Pet dander

However, they do not remove gases, odors, or volatile organic compounds (VOCs). For these pollutants, additional filtration methods, such as activated carbon filters, are necessary. (hepa.info)

Choosing the Right HEPA Filter

When selecting a HEPA filter, consider the following factors:

  • Filter Grade: HEPA filters are classified into grades based on their efficiency. For home use, a True HEPA filter (H13 grade) is recommended, as it captures 99.97% of particles at 0.3 microns. (cleanair.app)

  • Room Size: Ensure the air purifier is suitable for the size of the room where it will be used. Check the manufacturer's specifications for recommended room sizes.

  • Maintenance: Regular maintenance, including timely filter replacement, is crucial for optimal performance. Follow the manufacturer's guidelines for maintenance schedules.

Conclusion

HEPA filters play a vital role in improving indoor air quality by capturing a wide range of airborne particles. Understanding their function and selecting the appropriate filter can lead to a healthier indoor environment.

Highlights:

  • We spent over 800 hours testing the best air purifiers - here are our top 7, Published on Monday, June 15

Frequently Asked Questions