A high efficiency particulate air (HEPA) filter is a pleated device that can remove particles from surrounding air. A number of devices use these filters, such as air purifiers, which are designed to remove a host of particles and pollutants from the air in your home.
There is no federal certification or regulation for HEPA filters in the United States, but the Environmental Protection Agency offers some advice on how to choose efficient filters. Keep reading to learn some tips for choosing HEPA filters and how to find the best air purifier for your home.
HEPA filters remove tiny particles from dust, mold, pollen, bacteria, viruses, and more from the air. Thin glass fibers are randomly arranged into a dense, paperlike material that is folded into pleats to create the filter.
As air particles pass through these filters, pollutants are trapped in the fibers. Then, as larger particles stick to the filter, they keep other smaller particles from passing through. A HEPA filter can trap particles as small as 0.3 microns. For reference, the smallest thing the human eye can see is 25 microns, and a strand of hair is between 17 and 180 microns in diameter.
When placed into filtration systems like air cleaners and purifiers, HEPA filters can remove 99.97 percent of particles from the air. These filters were initially used in nuclear plants, but a host of new devices use this technology in products that can help clean the air in your home.
Types of filters
There are many kinds of air filters and air purification devices available for home use. HEPA filters can be used in cleaning devices, air filters, portable air cleaners, whole-home fan systems, heating and cooling units, and more. The goal is to filter tiny particles from the air as it passes through these devices.
HEPA filters aren’t the only way to do this, but they are recognized as highly effective, filtering some of the smallest particles from the air. Other examples of filters include:
- Ultra-HEPA filters or ULPA filters. These can trap up to 99.999 percent of particles 0.3 microns or smaller.
- Electrostatic filters. These trap particles using a small static charge, which help the particles stick to the filter.
- Electrostatic precipitators. These filters use metal plates or wires to attract particles with an opposite charge. They can often be washed and reused.
- Ionization. These filters rely on a small charge that emit a magnetic-like attraction to particles in the air. This type of filtration may release ozone gases and could cause irritation for people with respiratory diseases.
There are so many options when it comes to home air cleaning, and the choices can become overwhelming. While the EPA does not certify or recommend particular types of air filters, the agency does offer advice for selecting the right product for you. These recommendations were the basis of our selection process and include the following considerations.
- Size matters. Look for portable filters designed for the room size you are trying to use it in. Generally, the clean air delivery rate (CADR) score of your filter should be equal to about two-thirds of the area in the room.
- Avoid air cleaners that generate ozone. Ozone is a gas that is released during some air purification processes. While ozone gas is meant to clean and sanitize air, it’s also considered a pollutant that can cause irritation and damage to the lungs when inhaled. Air cleaners that use ozone are generally intended for rooms that are uninhabited at the time of use. They are not for use in confined spaces when you are present. No government agency in the United States has approved any ozone generators as air cleaners in homes.
- Look at industry ratings. While EPA doesn’t set rules for these filters, there are industry leaders that set standards for HEPA filtration. When purchasing a filter, it should meet one of the following criteria:
- designated HEPA filter
- CADR rated
- manufacturer states the product filters most particles smaller than 1 micron
How is filtration measured?
Clean Air Delivery Rate (CADR) is a way of measuring home air purifiers. It measures what sizes of particles can be removed in a volume of air, or how many cubic feet per minute can be filtered. The rating is assigned after testing small, medium, and large particle filtration — usually using smoke, pollen, and dust. How much of these elements are filtered per minute is measured, and a CADR score is assigned based on the results.
To decide what CADR rating you need, look at the size of the room you want to filter. The higher the CADR rating, the more particles the device will remove from the area, and the larger room it can service.
While CADR is the residential rating tool, industrial HEPA filters are usually measured with minimum efficiency reporting values (MERV) ratings that range from 1 to 16. The American Society of Heating, Refrigerating, and Air Conditioning Engineers developed this system. Higher values indicate better filtration power.
The price of an air purifier depends on the size, features, and how well it filters the air. Prices can range from $100 to thousands. On most commerce sites, you will be able to customize your search by filtration and price range to find the model that works best for your needs and budget.
We combed reviews and ratings from a number of home HEPA air purifiers, compiling a list that combined those ratings and feedback with the recommendations from EPA and industry leaders. Air cleaners that used ozone or ionization technology were excluded. The results are:
- CADR rating: 300
- Price (MSRP): $249.99
This device can usually be found in many brick-and-mortar stores and on sale, making it an easy choice to buy in a hurry — when it’s in stock. This machine is made to be portable and easy to move between rooms. It’s quieter than some of its competitors but still delivers great filtration.
Models built for smaller rooms or for moving a smaller volume of air can also be found, bringing price tags down. Consumers love this product, according to ratings, listing it as an affordable and effective device.
- CADR rating: 260
- Price (MSRP): $219.99
Levoit is a favorite on consumer-driven sites like Amazon, and offers a variety of models to fit every price range. The Core 400s is priced just below the range of other high performers, so it’s affordable but also does the job.
Named for the room size it’s designed to filter (400 square feet), the Core 400s features a large HEPA filter. Options for bells and whistles like voice control are also available, and the device is easily portable.
- CADR rating: 246
- Price (MSRP): $249.99
The Winix line also offers several models, but the 5500-2 is a performer for the budget conscious. There are no smart sensors or fancy apps with this model, but you can use automatic settings.
AHAM Verifide, a manufacturers’ association and product testing program, certified this air purifier’s performance for rooms up to 360 square feet.
- CADR rating: 350
- Price (MSRP): $299.99
Blueair actually makes it onto our list twice. Once for this air purifier that tops several “best HEPA air purifier” lists on consumer sites. Consumer Reports praises the model for having top-rated filtration at both high and low speeds (CADR scores are usually based on filtration at the highest speed only). The second time, below, is for its line of air purifiers overall, which gives an option for most room sizes and budgets.
This portable machine is designed for home use and has washable filter components to extend the life of your filter. This isn’t the quietest model, but it has other features, like a light to remind you when it’s time to change the filter.
One thing to keep in mind is that Blueair doesn’t use True HEPA filtration. They use a combination of physical filters and electrostatic charge, that they call HEPASilent.
The 16-pound machine has no handle or wheels.
There are other sizes available in the Blue line as well.
- CADR rating: 380
- Price (MSRP): $349.99
Medify Air is another popular brand, especially among those who need air purifiers for medical reasons. While it promises to be “quiet,” the quietest setting is about half the volume of a vacuum cleaner, making its noise level a matter of opinion.
This large unit could be difficult to move due to its design and size, but it delivers high levels of filtration for the price. There are a variety of models from this manufacturer to choose from.
- CADR rating: 241
- Price (MSRP): $329.99
BISSELL is a well-known name in filtration and the air320 purifier evokes the feeling of nostalgia with a retro furniture look. While the device can be portable, this might be difficult due to its size. The 20-pound device does come with a carrying handle, though. BISSELL offers a number of other models as well.
- CADR rating: 200
- Price range (MSRP): $549.95–$639.95
For people looking for style and function, Rabbit Air offers a well-reviewed — albeit expensive — option. These devices come in black and white, or a few famous art prints like Monet’s “Water Lilies” and Van Gogh’s “Starry Night.”
Extremely quiet on the lowest settings, you may sacrifice some function for volume and appearance with this model. CADR ratings are lower than some cheaper models, but if you’re looking for function and appearance with high-tech options, this model could suit your needs.
This is the only device on our list that gives you the option to either set it on a tabletop or mount it on a wall.
- CADR rating range: 200–640
- Price range: $350–$900
There are several models in the Blueair Classic line of air purifiers. These workhorses earn top ratings from a number of reviews, especially from people who need air filtration for allergies or asthma.
Some from this line are heavier models than Blueair’s Pure line, and a few have caster wheels to help make them portable. Reviews claim these are quieter than Pure at lower speeds, but can be loud at higher speeds. Still, these purifiers are quick and efficient at higher settings.
- CADR rating range: 150–350
- Price range (MSRP): $189.99–$749.99
This line features a variety of styles and colors, but the real draw is its filtering power. While the filtration power is high, though, so is the price. One of the pricier options on our list, the Coway devices feature extras like Wi-Fi connectivity, a mobile app, and voice control.
When choosing an air purifier, keep in mind that you should purchase your device based on room size and filtering ability. Also, the device can only filter as well as you maintain it. A dirty or expired HEPA filter will not do its job well. Check the manufacturer’s recommendation on filter replacement. Generally, these should be switched every 60 to 90 days.
You should also be sure to follow the manufacturer’s recommendations on placement, operation, and maintenance for best results.
Overall, consider why you want an air purifier, how well the device you are considering filters air, and your budget. Some units may have an attractive price, but it all comes down to how well a unit will filter the air in the size of the room you will be using it in.