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HEPA Air Filters Buying Guide

UNDERSTANDING HEPA FILTRATION: WHAT IT IS, HOW IT WORKS AND HOW IT CAN BENEFIT YOU

WHAT IS HEPA FILTRATION

High Efficiency Particulate Air, or HEPA, filters are a unique type of air purification. Achieving the most rigorous of requirements, for a filter to be labeled “HEPA” it must meet guidelines set by the US Department of Energy remove 99.97% of particles as small as 0.3 microns. When you buy a product that’s labeled HEPA, you know it’s been manufactured, tested, certified, and labeled in compliance with HEPA filter standards.

HOW HEPA AIR FILTERS WORK

When air is forced through the fine mesh of a HEPA filter, it captures airborne particles like pollen, pet dander, dust mite debris, and even tobacco smoke. The mesh filter is made of an extremely fine glass fiber that is able to trap particles using three different mechanisms:

Interception
Much like on the football field, interception with air filtration happens as particles in the airflow are captured. When the particles come within one radius of the filter, they adhere to its fibers and are trapped.
Impaction
Impaction happens when large particles floating in the airstream aren’t able to handle changes in airflow, so they crash into the filter fiber and become embedded in it.
Diffusion
Related to the concept of Brownian motion, or the random movement of microscopic particles and their interaction with surrounding molecules, diffusion happens when the unpredictable, zigzag motion of particles slows its travel through the HEPA filter and boosts the chance of getting trapped with interception or impaction.

WHY USE HEPA FILTRATION

Considered the gold standard of air purification systems, HEPA filters come highly recommended by allergy and asthma experts. The American College of Allergy, Asthma and Immunology explains, “for people with allergies, scientific studies have shown that air filtration reduces these airborne allergens and may provide some relief … look for an air cleaner with a HEPA filter.” Often used as a supplement to whole-house filtration systems, HEPA filters are especially useful during allergy season to trap any of the particles that made it past the heating and cooling system’s filter.

WHAT HEPA AIR FILTERS REMOVE

The powerful design of HEPA filters gives them the ability to trap airborne particles as small as 0.3 micrometers in diameter, including:

  • Lint dust
  • Pet dander
  • Mold spores
  • Pollen
  • Dust mites
  • Fine dust
  • Bacteria

HEPA FILTER STANDARDS AND REQUIREMENTS

HEPA filters must remove 99.97% of particles as small as 0.3 microns to meet guidelines set by the US Department of Energy. Unlike other filter rating systems like MERV and FPR, the HEPA rating only applies to air purifiers — it’s not used for furnace or air conditioner filters.

WHEN TO REPLACE YOUR HEPA AIR FILTER

Unlike its most air and water filters, HEPA filters perform better over time. They have a unique ability to improve with age and dirt, making it hard to know when it’s time for a replacement. Installing a clean filter is important because the trapped microorganisms can reproduce within the filter. While the general recommendation is to replace your HEPA filter every 6 months, following the manufacturer’s suggestion will ensure your filter is in peak performance and efficiency.

PROS AND CONS OF HEPA FILTERS

Pros
  • The most effective type of air purifier for allergy relief.
  • Once particles are captured in a HEPA filter, they will stay there and will not leak into the air.
  • HEPA efficiency increases as the filter gets dirty. Unlike traditional air filters that lose efficiency as they become dirty, dirtier a HEPA filter gets, the more efficient it becomes.
  • Small and portable, a HEPA filter can easily be moved between rooms of your home and take up very little floor space. An especially good option for apartments, you can clean your air without accessing the heating and cooling system
Cons
  • HEPA filters have a limited range of air they can treat. Not a whole-house solution, one HEPA filter system can typically clean the air of one room. Check the product description for the square footage it is able to handle.
  • To make their product sound compelling, some manufacturers will use terms like “HEPA-like” or “HEPA-type” to make their product seem as powerful as a HEPA filter. The products may be made with similar materials or remove a high number of particles, but they have not met the HEPA certification requirements and will not perform to the same standard. Look for labels that say “true” or “absolute” HEPA filters and specify “99.7% of particles at 0.3 microns.”
  • Sometimes considered noisy, a HEPA filter is a mechanical filter so it’s moving parts can create a noticeable sound while it works.
  • Once trapped in the filter, microorganism can breed or reproduce. Routine filter replacement can prevent increasing the number of microorganisms.