What is HEPA Air Purifier?

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Updated February 2, 2023

A HEPA air purifier is a type of unit with a filter destined to capture and remove large and small particles from the air. These models are available in many types and sizes to suit different room spaces.

HEPA stands for High-Efficiency Particulate Air and is a filter type that’s designed to adsorb air contaminants such as pet dander, pollen, tobacco smoke, mold, dust, and dust mites. This is exactly what the Winix Plasmawave 5500 does. It’s used extensively to improve indoor air quality, especially for environments that need to be scrubbed of allergens for people suffering from allergies and asthma. Check out the best air purifier for mold here.

If you have read about the air purifier reviews Cnet has, you’ll find a wider variety here.

What is HEPA Air Purifier Filter?

HEPA is a filter type, originally developed in the 1940s to reduce the probability of radioactive element contamination during the Manhattan Project.

HEPA Filter Definition:

A high-efficiency air filter designed with randomly arranged, fiberglass fibers. Also known as a depth filter, its porous design retains particulates of a specific size (depending on the filter grade), ensuring that they aren’t released back into the environment. Due to the nature of the design, these filters can hold a significant amount of waste before requiring replacement.

HEPA Filter
An illustration of the HEPA filtration process.

High-Efficiency Particulate Air (HEPA) cleaners help scrub indoor air to remove airborne waste. Sometimes these air cleaners combine filtration methods using HEPA in parallel with activated carbon filters, UV lights, and sometimes ionizers to further clean the air.

Can HEPA Air Purifier Filtration Help With Allergies?

Absolutely, but only when used in conjunction with other cleaning methods. HEPA air filters are highly effective at removing airborne particles that tend to irritate allergies, but that’s just one step in the battle against indoor air contaminants. Like all things airborne, many heavier components will settle on the ground, rather than stay suspended in the air. It’s important to thoroughly clean floors, especially carpets, bedding, and curtains, as these surfaces can retain pollutants.

Some vacuum cleaners have HEPA filters designed to contain these particles, so a good regime would be to use a HEPA air purifier in unison with a HEPA-grade vacuum cleaner. Other steps can be taken to increase allergen reduction in the home, including keeping pets outside, smoking outside, washing bedding frequently, replacing carpets with hardwoods or tile, and covering mattresses with plastic covers.

A home air purifier for mold, pollen, dust, smoke, and spores can be extremely effective at improving indoor air quality, but only if used properly and in conjunction with other steps to improve your home’s air.

Are There Different Classes of HEPA Filters?

Various HEPA filter classes are available, but typically United States HEPA filters adhere to a Department of Energy standard specifying the requirement to remove at least 99.97% of airborne particles with a radius of 0.15 micrometers. A common marketing term called “True HEPA,” is meant to signify that the filter has indeed passed regulatory requirements and is an actual HEPA filter.

Some brands may market their filters as “99% HEPA,” or “HEPA-style” and these should be avoided as they haven’t met adsorption requirements specified by the government standard. Another efficiency scale to look for is called the Minimum Efficiency Reporting Value (MERV), which measures the overall ability of a filter to remove particulates from the medium it’s treating. The scale ranges from 1 to 20, with higher ratings indicating better performance.

Most portable air purifier filters have a MERV rating between five and eight, while outstanding home purification systems fall somewhere between nine and twelve. Anything over a MERV of twelve is usually meant for industrial applications.

How Does HEPA Filtration Work?

HEPA filters use specialty interlaced fibers, designed in a way that maximizes surface area to adsorb the most contaminants possible with the smallest footprint. Differential pressure across the filter ensures that airflow is uni-directional, pulling contaminated air into one side and pushing purified air out of the other.

Depending on the specific filter design, gases are typically diffused into the filter itself, while larger particles get stuck on the individual fibers through what experts call interception and impaction.

The best HEPA air purifier will employ a high-grade HEPA filter with a MERV rating of nine or more. Home solutions for air cleaning vary greatly, but generally, consumers have two options: (1) Portable air purifiers, or (2) a Whole house HEPA filter.

Portable solutions are easier to install, but might not be powerful enough to treat an entire home – these are ideal for small spaces, bedrooms, or living areas.

Whole-house HEPA filters are installed as part of the overall home HVAC distribution system, are more difficult to install,  and usually require a greater initial investment. Other key terms to know for air purifiers include CADR and VOC meter. Knowing these two additional terms will help you locate the right air purifier to help with flu and remove other air contaminants.

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