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The best filter insert for masks

Which filter inserts for masks are best?

Cloth masks typically are the most affordable options for staying healthy and safe in crowded public settings because you can wash them and repeatedly wear them. However, you’ll get more protection from a cloth mask if you add a filter insert that provides extra layers to keep virus particles and other contaminants from getting through.

Filter inserts fit into the pocket between the layers of a cloth mask to help boost its filtration up to 35%. Not all filter inserts are created equal, though. Some offer more protection than others. If you want a high-quality set of reasonably priced filter inserts, the NBDIB PM 2.5 Activated Carbon Filter Inserts is the top choice.

What to know before you buy a filter insert


Filter inserts are designed for use with reusable cloth masks. However, if you mainly use other types of masks, the inserts generally aren’t compatible with them. For example, it can be challenging to layer a flat filter insert with a medical mask or KN95 mask without it moving around. As a result, the insert won’t improve the protection these masks offer. Don’t use filter inserts on their own; make sure you have a cloth mask in which to place the filter.


There isn’t any material or number of layers that can block 100% of virus particles from getting through a mask. The trick is to find a combination of layers and materials that allows you to breathe normally while reducing the number of particles that reach you.

Even when you’re wearing a mask with a filter insert, follow social distancing guidelines in crowded public spaces to limit exposure to viruses and reduce the chance of contracting and spreading them. For more information, check out the full filter inserts for masks buying guide at BestReviews.

What to look for in a quality filter insert


According to the Centers for Disease Control, filters should feature several layers of paper and/or cloth to keep airborne viruses and other particles from getting through. Most inserts have three to five layers. The roughest layer usually is at the center of the mask and may be infused with activated charcoal, which can effectively trap airborne particles.

Each layer in the filter insert should be different, though. Look for a filter that combines smooth outer layers with rougher inner layers to ensure it can keep small particles from getting through.

Materials and layers

Filter inserts can feature a few different material types, although all the materials usually are somewhat rough or fuzzy. That’s because smooth materials aren’t as effective at trapping airborne particles and droplets.

Polypropylene layers: The CDC recommends these be in a filter insert because they produce an electrostatic charge. This static helps contain droplets from both inside and outside the mask.

Activated carbon layers: This layer helps trap airborne particles such as dust, smoke and mold. They aren’t effective for trapping virus particles on their own, but they can work well as part of a layered filter.

High-efficiency particulate air filtration layers: These layers can help keep out up to 99% of particulates. However, they aren’t as breathable as a carbon filter. To ensure you’re protected, look for a filter labeled as HEPA and certified by the Institute of Environmental Sciences and Technology. Filters labeled as “HEPA-like” or “HEPA-type” generally aren’t as effective.

PM rating

Particulate matter (PM) describes the mixture of water droplets and solid particulates you can breathe in from the air. The particulates are different sizes, so larger, heavier particles such as smoke are visible while super-fine particulates are invisible to the naked eye.

The Environmental Protection Agency categorizes particulates that can be inhaled in the following sizes: PM10, which refers to particles 10 microns or smaller, and PM2.5, which refers to particles 2.5 microns or smaller.

Nearly all viruses are smaller than 2.5 microns, so you need a filter insert rated PM2.5 to effectively block them from reaching you.


A filter insert should fit easily within the pocket in your cloth mask. If it’s too large, it will fold inside the mask and create gaps. If it’s too small, it won’t cover the entire surface area, so particles may get in along the edges.

You can usually find filter inserts that are the same size as standard large and small cloth masks. If you have a specialty mask such as one designed for cycling, there are custom-cut filter inserts available.


When choosing filter inserts, purchase a set that’s as easy to use as possible. Some filters are more difficult to place inside a mask and straighten out for effective protection. Inserts with a smoother outer layer usually are the easiest to place in a mask because they don’t generate too much static and cling to the cloth.

Consider how much use you can get out of each filter insert. Some last for up to three days, which can be very convenient. However, it’s recommended you wash your mask after each use, so you’ll likely want to change your filter daily, too.

It helps to buy inserts in larger quantities. If you find a style that fits your masks well, you can save money by buying sets that contain 30-100 filters.

How much you can expect to spend on filter insert

You’ll usually pay between $3-$26 for filter inserts, depending on the pack size. A 10-pack of PM2.5-rated filters typically costs between $3-$5, but if you want filters that come in small and large sizes, expect to pay between $6-$12. A large pack with 50-100 filter inserts generally costs between $13-$26.

Filter insert FAQ

Is it worth it to use a filter insert if it doesn’t offer 100% protection against virus particles?

A. Studies suggest a two-layer cloth mask can block 70%-90% of virus particles on its own. If you add a five-layer, PM2.5-rated filter, you can reach protection of 95%-99%. That can make it much safer to go out in crowded public spaces if you’re concerned about getting sick.

Are filter inserts washable?

A. Filter inserts aren’t washable, so remove them from cloth masks before you wash the masks.

What’s the best filter insert to buy?

Top filter insert 

NBDIB PM2.5 Activated Carbon Filter Inserts

What you need to know: These simply designed five-layer mask inserts provide solid performance and an excellent price point for effective protection against many airborne contaminants.

What you’ll love: The inserts feature five layers, including particle-trapping activated carbon. The inserts are available in 20-, 50- and 100-piece sets. They ship quickly.

What you should consider: The filters can limit airflow too much to be comfortable for all users.

Where to buy: Sold by Amazon

Top filter insert for the money

KellyKessa Activated Carbon Filters

What you need to know: This set of five-layer filters offers one of the best prices, considering you get 100 extremely high-quality inserts that provide protection against viruses and more.

What you’ll love: The filters include activated carbon and non-woven melt blown cloth. The inserts are breathable, so they’re comfortable to wear. They can work with cloth masks that don’t have a filter pocket.

What you should consider: Some buyers find they’re too small to work well with large cloth masks.

Where to buy: Sold by Amazon.

Worth checking out

Yizer Adult PM 2.5 5-layer Activated Carbon Filter Inserts

What you need to know: These inserts aren’t just affordable but offer versatile protection against a wide range of airborne contaminants.

What you’ll love: Each set contains 100 filters. The inserts have five layers to effectively block particles. They work well to block pollen, smoke, pollution and dust in addition to virus particles. They’re well-sized, so they work with a variety of cloth masks.

What you should consider: They aren’t as breathable as some buyers would like.

Where to buy: Sold by Amazon.

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Jennifer Blair writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.

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