The most important things to know about your cloth face mask

Here are the most important things to have in a cloth face mask and why they are essential.

References: Stanford Medicine June 2020;  American Chemical Society published in June, 2020 ; Disaster Medical Public Health Preparation, 2013; Davies et al., 2013; Driessche et al., 2015; Stockwell et al., 2018; Leung et al.,2020; Mueller and Fernandez, 2020; Physics of Fluids 32, 061708 2020; Tang, Liebner, Craven, and Settles 2019; Leung et. al, 2020.See last tab of blog for more references with supporting evidence that face masks are effective in preventing transmission of viruses. 

Davies et al., 2013; Dbouk & Drikakis, 2020; Chughtai, Seale, and Macintyre, 2020; van der Sande, Teunis, & Sabel, 2008; New England Journal of Medicine, 2020; Wang, Ng, & Brook, 2020; Leung et. al, 2020; Lau, Tsui, Lau, & Yang, 2004; Wu et al., 2004; Dharmadhikari et al., 2012; Davies et al., 2013; Lai, Poon, & Cheung, 2012; MacIntyre et al., 2017; Offeddu, Yung, Low, & Tam, 2017; Davies et al., 2013; van der Sande, Teunis, & Sabel, 2008….. See last tab for more references with supporting evidence that face masks are effective in preventing transmission of viruses.

Filter Test

What does it mean?

Bacterial Filtration Efficiency

Bioparticle Filtration Emission (BFE)

Bioparticle Filtration Emission indicates filtration efficiency. The higher the percentage, the higher the efficiency. For example, 95% BFE indicates 5% of the aerosolized bacteria used in testing passed through the mask material, while 99.7% BFE indicates only 0.3% passed through.

Particle Filtration Efficiency

(PFE)

Particle Filtration Efficiency measures the filtration efficiency of filter fabric against µm (sub-micron particles and aerosols).

Delta P

Differential Pressure

Pressure Drop

Pressure Loss

(PSID)

Measures the effort it takes to force air through material. Essentially, how easy it is to breathe. The lower the Delta P, the more breathable and comfortable the mask.

Fluid Resistance

(FR)

Fluid resistance of face masks is measured by spraying synthetic blood at various levels of pressure (80, 120, 160 mm). The higher the pressure withstood, the greater the fluid spray and splash resistance. Results are displayed as either a pass or fail for each level of pressure.

Flammability

Basically, fabric is set on fire in a controlled environment for a predetermined time and characteristics such as time to ignition, flame spread (propagation rate) and characterization of the residue are determined. Based on that information, the fabric passes certain levels of flammability safety.

Who conducts filtration tests? Who approves or certifies the tests? These two questions are best answered together. Fabric manufacturers use individual labs and research centers to test their materials. Then the manufacturer submits the test results for particle filtration efficiency, bacterial filtration efficiency, fluid resistance, differential pressure, and flammability for approval and certifications. Certification standards are set by different organizations. For example, ASTM International is one of the world's largest standards developing organizations. They have a series of tests that categorize masks into levels (1, 2, 3) and they grant certifications based on efficiency. The National Institute for Occupational Safety and Health (NIOSH) is another research center. The Occupational Safety and Health Act of 1970 established the National Institute for Occupational Safety and Health (NIOSH) which is part of the U.S. Centers for Disease Control and Prevention, in the U.S. Department of Health and Human Services. NIOSH provides a testing, approval, and certification program ensuring respirators, PPE and N95 masks used in the workplace meet certain safety standards. Furthermore, the FDA clears surgical masks based on manufacturer-submitted test data and proposed claims.3 

Common tests include EN14683:14 and Level Barrier in ASTM F2100-11. These tests require certain levels of particle filtration efficiency, bacterial filtration efficiency, fluid resistance, differential pressure, and flammability to be considered EN14683:14 and/or ASTM F2100-11 certified. If a material has one of these certifications it means that it has a Bacterial Filtration Efficiency BFE >95% (high filtration) and a Differential Pressure rate of 3-5mm H20/cm2 (meaning it’s breathable) and/ or the following: a PFE <95%, Fluid Resistance of 80mmHg, microbial cleanliness  <30 cfu/g. Kade & Vos face mask filters have passed EN14683 testing.

The best type of filter is a non-woven polypropylene (which is what we use in our masks). This material is used in medical and surgical face masks. Some Meltblown components have an equivalent rating of Bacterial Filtration Efficiency (BFE) 95% per ASTM F2101 and EN 14683.

I recommend buying them from actual fabric filtration suppliers. While products on Amazon can ship quickly, not all sellers are honest in their offering. A medical grade fabric supplier is required to have their materials tested before making any claims and selling them to the public. This way you can make sure the material you are using is safe. 

Here are a few USA non-woven polypropylene suppliers including some that Kade & Vos uses for our filters:

Air Filters Incorporated

Protective Gear Technologies

SuperHuman Streetwear -$7.90/ yard with BFE >95%

MaskBond PFE>90%

If you’re in a pinch, you can use a reusable grocery bag that is also made of non-woven PP. One lab found that 2 layers of a grocery bag provides 34% filtration efficiency. Used as a filter inside a mask made of high thread count cotton is sure to provide adequate protection because 2 layers of cotton fabric provides between 69%-74% filtration efficiency.

Here are what a few other studies found about the BFE and pressure drop of common household items as filters.

Material

Results

Oil Only Sorbent Pads

(made of polypropylene)

1 layer of it captured 35.02% of particles and it had a pressure drop of 2.67 mm H20.

(* indicates results from Michigan Mask Response Research study).

Meltblown Polypropylene (PP):

Meltblown PP with a pore diameter between 28-40μm (micrometer)  captured 86.86-88.64% of particles (an N95 captures 95%+) and it had a pressure drop of 7.7 mm H20 (an N95 is 9 mm H20). MPP provides high filtration efficiency while still being easy to breath in (Xiao, 2019).

Reusable polypropylene grocery bags

One study found that 2 layers captured 34% of particles (an N95 captures 95%+) and it had a pressure drop of 96 (a surgical mask is 140).

Coffee filters

As it turns out 2 layers of coffee filters are hard to breathe through and don’t filter particles well. The coffee filter in this study captured 14.1% of particles (an N95 captures 95%+) and it had a pressure drop of 16.42 mm H20 (an N95 is 9 mm H20), making it very difficult to breathe.*

Fusible Interfacing

Its filtration captured 17.24% of particles and was very easy to breathe through with a pressure drop of 1.08 mm H20. An N95 is normally 9mm H20.*

It captured 80.85% of particles and had a pressure drop of 8.15 mm H20 (an N95 is typically 9 mm H20).*

However, most furnace filter companies are saying they don’t support people using their furnace filters in masks. It’s not designed for this use, so they don’t know how safe it is.

2 layers captured 34.94% of particles and had a pressure drop of 0.95 mm H20 (an N95 is typically 9 mm H20).*

1 layer captured 68.48% of particles and had a pressure drop of 10.82 mm H20 (an N95 is typically 9 mm H20).There are mixed opinions about the safety of vacuum bags. In my opinion, there is not enough research about having vacuum bag chemicals close to the face. *

They’re made from paper waste, tree fibers, and synthetic latex resin. The study tested shop towels made by Toolbox. 2 layers of it captured 41.94% of particles.* A Home Depot representative says that the shop towel is designed for cleaning and would not recommend or advise anyone to utilize it for face masks.

1 layer captured 39% of particles and had a pressure drop of 11.5 mm H20 (an N95 is typically 9 mm H20).*

4 layers of Viva paper towels captured 22.54% of particles.*

1 layer captured 14.8% of particles and had a pressure drop of 1.97 mm H20 (an N95 is typically 9 mm H20).*

2 layers captured 35.8% of particles and had a pressure drop of 6.1 mm H20 (an N95 is typically 9 mm H20).*

2 layers captured 57.56% of particles and had a pressure drop of 11.2 mm H20 (an N95 is typically 9 mm H20).*

You can also hold your mask up to the light and you shouldn’t be able to see any visible pores or dots of light coming through (Divya, 2016; Amutha, 2016). The image below shows many pores and dots of light pouring through.

Lastly, check the fit. Does it fully cover your nose and chin? Is it fitted close to your face on the sides, nose and chin without any major gaps? If yes, then your mask is most likely sufficient. These must fit tightly to the user’s face.2

• 3 layers
• With at least 2 of the 3 layers made of 100% cotton
• 1 filter layer
• A wire across the nose bridge
• Elastic or adjustable elastic ear-loops
• As for the best style of mask, one study found that the most protective design for adults is a minimum width of 8” across the face and a minimum height of 6” with pleats along the side

In a study from April 2020, researchers at Northwestern University compared the effectiveness of both commercial and cloth face masks. The researchers used an instrument that reports particle counts in the air from both the inside the mask and the surrounding air just outside the mask. They tested 3 commercial grade masks and 9 Cloth Face Masks. The cloth face masks varied in the number of fabric layers, fabric type, the measurements, if there was pleating or gathering on the sizes and if there was a nose wire.

Below is a summary of the findings:

Surgical Mask

96.35%

Somewhat easy

Should be reserved for medical professionals.

Vacuum Cleaner Bag

94.35%

Hard

High Filtration but stiff and difficult for inhalation. Vacuum cleaner bags also include a health warning indicating that it contains carcinogens and teratogens, so these types of masks or filters would not be suitable for face masks. 

Tea Towel

83.24%

Somewhat hard

Tea Towels are a strong fabric with a thick weave and show relatively high filtration efficiency but it was found difficult to inhale. Not recommended for face masks.

Cotton/ Polyester Blend

74.60%

Somewhat easy

Cotton blends have an excellent balance of FE and breathability. It is the most recommended material for cloth face masks.

One layer 100% cotton t-shirt

69% -70% 

Easy

The slightly stretchy quality of the t-shirt made this a more preferable choice for a face mask and it was considered likely to provide a better fit.

Antimicrobial Pillowcase

(polyester)

65.62%

Somewhat easy

Scarf

62.30%

Easy

Pillowcase

61.28%

Easy

Linen

60%

Easy

Silk

58%

Easy

One study looked at mask types and how far droplets traveled. When wearing a bandana, droplets made it through the fabric and traveled up to 3 feet, 7 inches. The bandana below is folded twice and secured with rubber bands around the ears.

With a scarf wrapped around the face, droplets made it through the fabric and traveled 1 foot 3 inches. A stitched cotton mask was the best material according to this study. According to the scientists' findings, a stitched quilted cotton mask proved most effective as droplets only traveled 2.5 inches through the material.

According to the data, some cotton masks seemed to perform even better than what the researchers described as a "professional-grade face mask." It's still worth noting that something is more effective than wearing no mask at all.

1. A trip to the grocery store.
2. A ride on public transportation.
3. A visit to your doctor.
4. Close interactions with others while you’re on the job, if you are an essential employee.

• to avoid transmission of infectious organisms and 
• to protection from air pollution (Choudhry et al., 2006).

Considering all the reasons that some individual are resistant to wearing face masks, Kade & Vos has made it our mission to do the following:

Not wearing masks because:

Kade & Vos is helping by:

Not comfortable 8, 9

Design masks that are comfortable

Difficulty breathing 8, 9

Design masks that provide protection AND are breathable

Don’t believe it is effective 10, 11, 12

Share information about the effectiveness of wearing masks

Availability 11, 12, 13, 14

Provide one of the most affordable, washable and reusable masks on the market.

Donate cloth face masks to our community

Proper training on how to wear one 11, 12, 13, 14

Provide resources for how to properly wear a face mask

Contradicting Government and Healthcare Policies 11, 12, 13, 14

Share the most recent CDC policies

Similarly, studies looking at smaller gatherings found that the more a person knows about the risks of infectious diseases the more likely they are to wear a mask. 10, 11, 12. How awesome is that! Once again education is found to be helpful!

Does showing someone how to wear a mask really increase the likelihood that they will wear one? Yes. 8, 15, 16, 17, 18. 

Does giving someone a free mask increase the likelihood they will wear one? Yes. People are 83% likely to wear a mask if it is for free 8, 15.  

There are also cultural differences to consider. One study looked at coronavirus deaths across 198 countries and found that those countries with cultural norms or government policies in favor of mask-wearing had lower death rates (Leffler, et. al, 2020 - Department of Ophthalmology, Virginia Commonwealth University).

References:

1. Canini et al., 2010
2. Cowling et al., 2009
3. Cowling et al., 2008
4. Larson et al., 2010
5. MacIntyre et al., 2009
6. Suess et al., 2012
7. Simmerman et al., 2011
8. Barasheed et al., 2014
9. Alqahtani, Sheikh, Wiley & Heywood, 2015
10.  Albano, Matuozzo, Marinella & Giuseppe, 2014
11. MacIntyre & Chughtai, 2015 
12. Nichol et al., 2013
13. Gershon et al., 1995
14. Lau et al., 2004
15.  Abdin, Choudhry, & Al-Naji, 2005
16.  Aljoudi, Nooh, & Jamil, 2004
17. Al-Zahrani, Chaudhry & Alhamdan, 2006
18. Deris et al., 2010

“Cloth masks will not lead to hypoxia. Surgeons operate for hours wearing them. They don't get these problems," says Infectious Disease Expert Professor Keith Neal.

The WHO says: "The prolonged use of medical masks when properly worn, does not cause CO2 intoxication nor oxygen deficiency.

“There is no risk of hypercapnia (CO2 retention) in healthy adults who use face coverings, including medical and cloth face masks, as well as N95s,” Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital, New York, told Healthline. “Carbon dioxide molecules freely diffuse through the masks, allowing normal gas exchange while breathing.”

“Rebreathing tiny amounts of CO2 from wearing either properly fitted N95 respirators or more loosely fitted cloth or surgical masks is of no concern for the vast, vast majority of people,” said Darrell Spurlock Jr., PhD, RN, the director of the Leadership Center for Nursing Education Research at Widener University and a professor in Widener’s PhD in Nursing program.

They recommend washing your mask in the washing machine or by hand. 

Washing machine

• You can include your face covering with your regular laundry.
• Use regular laundry detergent and the warmest appropriate water setting for the cloth used to make the face covering.
• Opt for non-scented detergent if you’re sensitive to scents.

Washing by hand

• Hand wash with a bleach solution. First, check to see if your bleach is intended for disinfection and make sure your fabric won’t be ruined.

Mix the following:

• 5 tablespoons (1/3rd cup) household bleach per gallon of room temperature water or
• 4 teaspoons household bleach per quart of room temperature water

• Soak the face covering in the bleach solution for 5 minutes.
• Rinse thoroughly with cool or room temperature water.

You can dry your mask in the dryer on the highest heat setting or air dry laying flat. If possible, let it dry in direct sunlight. Make sure it’s completely dry after washing and before wearing.

Johns Hopkins Medicine also says that we should wash our mask every time we wear it. 

• Bandanas, face scarves and masks made of fabric, such as cotton, can be washed in your regular laundry using hot water.
• Disposable, blue surgical masks cannot be laundered or cleaned and should be thrown away when it is visibly soiled or damaged.
• After laundering your fabric masks, tumble dry them in the dryer on a high setting.
• You can also hand wash your mask, using hot, soapy water. Scrub the mask for at least 20 seconds, and dry them on high heat in the dryer.

• Rothe C, Schunk M, Sothmann P, et al. Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany. The New England journal of medicine. 2020;382(10):970-971. PMID: 32003551
• Zou L, Ruan F, Huang M, et al. SARS-CoV-2 Viral Load in Upper Respiratory Specimens of Infected Patients. The New England journal of medicine. 2020;382(12):1177-1179. PMID: 32074444
• Pan X, Chen D, Xia Y, et al. Asymptomatic cases in a family cluster with SARS-CoV-2 infection. The Lancet Infectious diseases. 2020. PMID: 32087116
• Bai Y, Yao L, Wei T, et al. Presumed Asymptomatic Carrier Transmission of COVID-19. Jama. 2020. PMID: 32083643
• Kimball A HK, Arons M, et al. Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020. MMWR Morbidity and mortality weekly report. 2020; ePub: 27 March 2020. PMID: 32240128
• Wei WE LZ, Chiew CJ, Yong SE, Toh MP, Lee VJ. Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020. MMWR Morbidity and Mortality Weekly Report. 2020;ePub: 1 April 2020. PMID: 32271722
• Li R, Pei S, Chen B, et al. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science (New York, NY). 2020. PMID: 32179701
• Furukawa NW, Brooks JT, Sobel J. Evidence Supporting Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 While Presymptomatic or Asymptomatic [published online ahead of print, 2020 May 4]. Emerg Infect Dis. 2020;26(7):10.3201/eid2607.201595.
• Oran DP, Topol Prevalence of Asymptomatic SARS-CoV-2 Infection: A Narrative Review [published online ahead of print, 2020 Jun 3]. Ann Intern Med. 2020;M20-3012. PMID: 32491919
• National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020). Washington, DC: The National Academies Press. https://doi.org/10.17226/25769
• Schwartz KL, Murti M, Finkelstein M, et al. Lack of COVID-19 transmission on an international flight. CMAJ. 2020;192(15):E410. PMID: 32392504
• Anfinrud P, Stadnytskyi V, Bax CE, Bax A. Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering. N Engl J Med. 2020 Apr 15. doi:10.1056/NEJMc2007800. PMID: 32294341
• Davies A, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A. Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Disaster Med Public Health Prep. 2013;7(4):413-8. PMID: 24229526
• Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, Guha S. Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano. 2020 Apr 24. PMID: 32329337
• Aydin O, Emon B, Saif MTA. Performance of fabrics for home-made masks against spread of respiratory infection through droplets: a quantitative mechanistic study. medRxiv preprint doi: https://doi.org/10.1101/2020.04.19.20071779, posted April 24, 2020.
• Ma QX, Shan H, Zhang HL, Li GM, Yang RM, Chen JM. Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2. J Med Virol. 2020. PMID: 32232986
• Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al.Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med. 2020. PMID: 32371934
• Johnson DF, Druce JD, Birch C, Grayson ML. A quantitative assessment of the efficacy of surgical and N95 masks to filter influenza virus in patients with acute influenza infection. Clin Infect Dis. 2009 Jul 15;49(2):275-7. PMID: 19522650
• Green CF, Davidson CS, Panlilio AL, et al. Effectiveness of selected surgical masks in arresting vegetative cells and endospores when worn by simulated contagious patients. Infect Control Hosp Epidemiol. 2012;33(5):487‐494. PMID: 22476275