HEPA Filter Buying Guide: How HEPA Air Filters Work
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.
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.
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.
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 systems 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.
WHY 0.3 MICRONS?
The 0.3-micron test size isn't random. It is close to the most penetrating particle size (MPPS), the particle size that is hardest for a filter's fibers to catch. Larger particles are stopped by interception and impaction, and smaller ones by diffusion, so a true HEPA filter captures both larger and smaller particles at even higher efficiency than its 99.97% rating at 0.3 microns.
HEPA VS. MERV FOR YOUR HVAC SYSTEM
Most residential furnaces and air conditioners aren't built to push air through a true HEPA filter; the dense media restricts airflow and can strain the blower. For whole-home filtration, most homes are better served by a MERV 11 to 13 furnace filter, with a portable HEPA air purifier in the rooms where you want the cleanest air, such as bedrooms. Homes that want HEPA-level filtration throughout usually need a dedicated bypass HEPA system installed by an HVAC professional.
Shop air filters | MERV ratings explained
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 manufacturers suggestion will ensure your filter is in peak performance and efficiency.
HEPA OPTIONS
HEPA Rated Filter:
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
- 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 99.97% 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.