Learn the pros and cons of various types of materials and fabrics currently being used in face mask filters, and whether or not you need one at all in your DIY face mask.

Several weeks ago, my brother-in-law — who is a respiratory therapist at our local hospital — contacted me to make a pattern for . I made a pattern, tutorial, and step-by-step video, and it’s helped hundreds of thousands of people create their own homemade face mask. A couple of days ago, the CDC issued a statement recommending everyone wear cloth face coverings in public settings (e.g., grocery stores and pharmacies). Since then, we’ve been getting a ton of questions about making DIY face masks, including what sort of filter — if any — to include. So let’s talk about DIY Face Mask filters materials, and whether or not you need one at all.

My free pattern to make your own DIY face mask

Important Note: As research and testing continues into face mask filter materials, I will update this list to help you make the most informed decision for your DIY face mask making efforts. It’s critical to note that a material’s inclusion on this page does NOT make it suitable. I’m simply gathering evidence-based research and manufacturer’s safety sheets to help you make a more informed decision.

Looking for my DIY face mask tutorial?

Note: In my video which I made two weeks ago, I mentioned using a HEPA air filter and a HEPA vacuum cleaner bag filter, HOWEVER, since then new information has come to light that calls into question their safety and I no longer recommend these items, and won’t until I have definitive evidence that these DIY filter materials are safe. Read more below.

Do I really need a filter in my DIY face mask at all?

The CDC’s sewn cloth face covering materials list (see the CDC’s Cloth Face Covering information and material suggestions) calls for just two layers of “cotton fabric.” My research backs this up. A Cambridge University study in 2013 tested the effectiveness of homemade mask materials. Their conclusion was that one layer of cotton T-shirt material and one layer of tightly woven cotton fabric (like a pillowcase) was a better combination, and would each capture 61-69% of 1-micron particles, which is smaller than what we produce when we cough or sneeze (Atkinson, 2009). The study found that a homemade face mask was MUCH better than no mask at all.

The Cambridge University researchers said, “The pillowcase and the 100% cotton T-shirt were found to be the most suitable household materials for an improvised face mask. The slightly stretchy quality of the t-shirt made it the more preferable choice for a face mask as it was considered likely to provide a better fit.” (Davies, Thompson, Giri, Kafatos, Walker, Bennett, Allan, 2013)

Additionally, “The filtration efficiency of improvised fabric materials is comparable to some commonly used Federal Drug Agency-cleared surgical masks and unapproved dust masks” (The Annals of Occupational Hygiene, Volume 54, Issue 7, October 2010, Pages 789–798,

My with its optional filter pocket (but without a filter in place) has three layers. The Cambridge University study shows that two or more layers of cotton would increase the mask’s effectiveness to 74%.

Conclusion: Two or more layers of cotton fabric is 74% effective, and the safest, simplest option for a DIY face mask. When in doubt, skip the filter.

UPDATE: Looking for something more formal? Check out “Face Masks Against COVID-19: An Evidence Review” published on April 12, 2020 by 19 scientists. Their review gathers together available evidence at the time of its publication to help when developing policy around use of non-medical masks in public. It’s not yet peer reviewed as it just came out, but it’s an excellent overview of where we stand right now with face mask efficacy.

What filter do you put in a DIY face mask?

There are a lot of filter materials being suggested on the Internet, and not all of them are safe nor breathable. The Cambridge University study made an important point about the role of breathability and comfort, saying, “If respiratory protection is not capable of accommodating the breathing demands of the wearer, then the device will impose an extra breathing load on the wearer, which is especially impracticable for people with breathing difficulties. Furthermore, the extra breathing load may induce leakage owing to the increased negative pressure in the face mask.”

A mask that a person cannot breathe through is ineffective and dangerous. So we must look at both filtration effectiveness and breathability when determining whether a filter material is appropriate for a face mask.

What follows is a list of filter materials folks have asked me about and the research, if any, I could find on their effectiveness and breathability. It’s important to note that very little scientific research has been done at this point on these materials as filters. I’m hoping this changes in the coming weeks and months, and I’ll be watching and updating this page. Please always read the Material Safety Data Sheet, when available, and do your own research.

Coffee Filters

The CDC’s bandana face covering material list calls for a coffee filter as the second layer (the first layer being the bandana). The CDC does not indicate that the coffee filters are included for particle filtration, however.
Availability: You can find typically coffee filters at grocery stores and online.
Filter Effectiveness Research: Currently, I can find no published and peer-reviewed scientific research that supports coffee filter filtration effectiveness. However, some testing has begun and preliminary tests indicate it could provide about 40-50% filtration with multiple layers.
Filter Breathability: Poor. Coffee filters are very difficult to breath through.

Blue Shop Towels

According to Business Insider, a blue shop towel made from polyester hydro knit was found to be more effective as a DIY face mask filter than other household materials. They claim that two blue shop towels inserted into an ordinary cotton mask brought filtration up to 93% of particles as small as 0.3 microns. The two brands they tested were ToolBox’s Shop Towel and ZEP’s industrial blue towel. Note that Scott’s pro shop towels didn’t work as well. Unfortunately, I cannot find any actual data on this research other than the quotes in Business Insider. When and if their findings are made public, I will link them here. My understanding is they are raising funds to send their DIY face mask made with blue shop towels to a research facility for scientific testing. Until this test is conducted, we do not know for sure if this is an effective material.
Availability: You can find typically find blue shop towels at home improvement and online (BUT, supplies have been low recently).
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports blue shop towel filtration effectiveness. 
Filter Breathability: Good. 

Paper Towel

If blue shop towels work, what about regular paper towels. My research indicates paper towels are not effective. Two layers of paper towels were tested with a particle counter to see how well they filtered out .3 micron particles. Unfortunately, the two layers of paper towels were only able to capture 33% of the .3 micron particles (and on layer only managed to get 23%). That said, this would be better than nothing if you had no other alternative.
Availability: You can find typically find paper towels at grocery stores and online (BUT, supplies have been low recently).
Filter Effectiveness Research: See />
Filter Breathability: Good. 

Interfacing

Interfacing is used to stabilize fabrics when cutting and sewing. Currently, “non-woven” interfacing is being recommended by some as an option for filter material, specifically Pellon interfacing 380, 808, 810, 830, 880F, 910, 911FF, 930, 931TD, 950F, and Oly-Fun by Fairfield. Unfortunately, I can find no research that indicates whether interfacing is at all effective.
Availability: You can find interfacing at fabric stores, some craft stores, and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports interfacing filtration effectiveness. 
Filter Breathability: Ok to poor. Interfacing can be hard to breath through. The Pellon 808 I tried seemed tolerable, but perhaps not for long periods of time.

Cotton Batting (Quilt Batting)

Batting is used to increase the thickness and warmth of quilts, coats, and things of that nature. I can find absolutely no evidence that supports that it provides any effectiveness at filtration — it is not closely woven and I can’t see how it would do anything other than make a mask hot and too thick for comfort. I do not recommend you use batting.
Availability: Cotton batting is at fabric stores, some craft stores, and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports cotton batting filtration effectiveness. 
Filter Breathability: Not great (and hot).

Dryer Sheets

Dryer sheets are typically nonwoven polyester fabric covered with chemicals to help soften clothes and reduce static cling, as well as fragrances. While nearly all of the chemicals commonly found in dryer sheets are generally recognized as safe (GRAS) by the Food and Drug Administration (FDA), that does not mean they were tested as safe for use as face mask materials. Given that they are coated in chemicals and fragrances, I feel this would be a poor choice as a filter.
Availability: Dryer sheets are typically at grocery stores and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports cotton batting filtration effectiveness. 
Filter Breathability: Ok.

Felt

Felt can be made of wool (uncommon these days) or from synthetic fibers such as petroleum-based acrylic or wood pulp-based rayon (more typical, especially in “craft felt”). These different materials will behave differently, so it’s important to know what you have. Natural fiber felt will be more breathable and collect less condensation than synthetic fiber felt. According to the Reusability of Facemasks During an Influenza Pandemic: Facing the Flu, “Respirator and medical mask filters are typically composed of mats of nonwoven fibrous materials, such as wool felt, fiberglass paper, or polypropylene. The material creates a tortuous path, and various mechanisms result in the adhesion of particles to the fibers without necessarily blocking the open spaces, still allowing air to flow easily across the filter (Revoir and Bien, 1997).” Based on this information, a dense wool felt could do some good, but it unclear how much.
Availability: Felt is found at craft stores and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports felt’s filtration effectiveness. 
Filter Breathability: Ok.

Sanitary Napkin

A sanitary napkin (aka maxi pad) is for use by individuals who are menstruating. Unfortunately, they are saturated with chemicals, as well as a substance which swells and jells when it gets moistened to help the contents to stay put. You do not want to inhale those chemicals.  I do not recommend this material, and I feel it would be a poor choice as a filter.
Availability: Sanitary napkins are typically at grocery stores and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports sanitary napkin filtration effectiveness. 
Filter Breathability: Poor.

Wet Wipe

Wet wipe and baby wipes are pre-moistened towels usually at least partly made of woven polyester. They are saturated with chemicals ranging from gentle cleansing ingredients to alcohol-based “cleaners”. I do not recommend this material, and I feel it would be a poor choice as a filter.
Availability: Wet wipes/baby wipes are typically at grocery stores and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports wet wipe filtration effectiveness. 
Filter Breathability: Ok.

Halyard 600 Medical Grade Fabric

Halyard H600 is a two-ply spun polypropylene used by hospitals to wrap surgical instrument traps, and it cannot be penetrated by water, bacteria or particles. According to the manufacturer’s specifications, it blocks 99.9% of particulates, making the masks about 4% more effective at blocking particulate material than the N95 masks (this figure is from Bruce Spiess, M.D., a professor of anesthesiology at the University of Florida College of Medicine).
Availability: Unfortunately, this material is hard to come by if you do not work at a hospital. I do see it online for sale at Amazon, but I doubt it will stay available for long (and it’s expensive).
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports using Halyard 600 as a face mask filter, but the manufacturer’s specifications indicate it may be effective. This material’s safety is unknown however.
Filter Breathability: Unknown (I have none to try breathing through)

HEPA Vacuum Cleaner Bag Filters

The Cambridge University study tested vacuum bags filters for their ability to filter out 1 micron particles, and found them to be 94.35 percent effective. Unfortunately, they did not test or address the safety of using vacuum cleaner bags as filters, as my research shows that some of these vacuum cleaner bags could contain materials that are harmful if inhaled. They are also super hard to breathe through. So despite the Cambridge University study, I will not be using these in my masks (which is fine because I have none of these anyway).
Availability: Hard to get right now
Filter Effectiveness Research: The Cambridge University study in 2013 found them to be 94% effective against 1 micron particles
Filter Breathability: Poor. Vacuum cleaner bag filters are very difficult to breath through.

3M Filtrete HEPA Air Purifier Filters (MPR 1500 and above)

Accordion-style air filters typically used for home air filtration were first recommended as a DIY face mask material by Chinese mask makers during their outbreak earlier this year. According to the manufacturer’s specifications on their web site, HVAC air filters with an MPR of 1500 or above are 54%-77% effective at capturing small particles like bacteria and particles that carry viruses, whereas Filtrete Air Purifier Filters (True-HEPA Air Filter and HEPA-Type Air Filter) are 93%-99.97% effective (this data is based on ASHRAE 52.2 testing for .3 to 1 micron particles). Despite information widely circulating, these Filtrete air filters are NOT fiberglass. You can read the Material Safety Data Sheet here. That said, the manufacturer has specifically said on their site, “Our filters are designed to be used in HVAC systems, and the filter media has not been tested to be used as a face mask for respiratory protection. Altering any of our 3M Filtrete Air Filters is not recommended or supported by 3M or the Filtrete Brand. Customer safety is our number one priority.”
Availability: You can find air filters at home improvement stores and online.
Filter Effectiveness Research: None. Currently, I can find no published scientific research that supports using HEPA air filters as a face mask filter material and the manufacturer specifically stated on their web site that  “filter media has not been tested to be used as a face mask for respiratory protection.”
Filter Breathability: Good.

Air Filtration Filters (PM 2.5)

Air Filtration filters are intended for air pollution and dust, and are used as replaceable filters in respirators and masks. The question is — are they effective against small particles that can carry viruses?  Researchers from the University of Edinburgh tested different common masks and used a particle counter to see how many particles made it through a mask with a PM 2.5 air filter. They found that dust respirators with filters rated for PM 2.5 were about 97%-98% effective.
Availability: Available online, but often do not ship for some time.
Filter Effectiveness Research: . 2009;6:8. Published 2009 Mar 13. doi:10.1186/1743-8977-6-8
Filter Breathability: Good.

Can filters be washed? How often should they be changed?

If you choose to use a material as a filter, you should not attempt to wash it. There is no research to suggest this would not damage the effectiveness of a material. Instead, you should properly dispose of it and replace it at least daily.

For my personal DIY face masks, I’m sticking with multiple layers of 100% cotton, including heavyweight T-shirts, until I see compelling scientific evidence on the effectiveness and safety of another filter material. When and if I find that, I will update this page.

How do you even make DIY face masks?

Get my free pattern to make your own DIY face mask, with or without a filter!

Are you making cotton face masks? We’d love to see them! Please post over in our — everyone is welcome! We’d love to see your Cricut face masks, too! Please share them in the group or email us at hello@jennifermaker.com.

Love,

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