Homemade Cloth Face Masks: Peer-reviewed Scientific Information, Part 1

1918-2013: History & Limited Research Scope

This material was put online April 2020 and revised May 2020.
This webpage is one portion of the greater exploration entitled "Cloth Face Masks: Merging Science & Home Remedies" that can be access at https://clothingtextiles.ualberta.ca/facemasks/.

 

I found several scholarly articles that foresaw what we are currently dealing with but, as they were not done by textile scientists, the authors did not always understand the language of textiles. Nonetheless, we can learn certain things through those sources, one of which traces the history of face masks and is useful to address home remedies. One source explains that, “[s]ince the development of surgical masks and respirators, very little research has been conducted on cloth masks recently.” (Chughtai, Seale, and MacIntyre, 2013: 3). As we are not concerned with surgical masks and respirators in the current research project because such devices function fairly well, going back to historical remedies may be of value simply because commercially available, tested products are in very short supply in the face of the global COVID-19 pandemic.

The focus here is “cloth” face masks made at home. “Cloth” is a broad term used for both woven and non-woven textiles, of which there are many varieties. Authors do not address in great detail (or at all) what they mean by “cloth,” which is problematic. For instance, a very loose weave structure will allow many more particles through a mask compared with a tightly-woven structure. Additionally, none of the scientific articles read thus far address the strengths and limitations of woven and non-woven textiles.

Here is information gathered from my reading that first address the pros and cons of cloth face masks and, afterwards, specific pieces of information that should be of use when designing and making cloth face masks.

 

2A. Pros & Cons

PROS

  • CLOTH MASKS MAY OFFER SOME VALUE COMPARED WITH NO PROTECTION
    “Thus, the use of improvised fabric materials may be of some value compared to no protection at all when respirators are not available.” (Rengasamy, Eimer and Shaffer, 2010: 796)
  • CLOTH MASKS AS A COMPONENT OF SEVERAL MEASURES MAY BE BETTER THAN A SINGLE METHOD
    “The authors concluded that a combination of several measures including the use of respiratory protection devices, gloves, and other hygienic practices may reduce the spread of infectious diseases considerably than by a single method.” (Rengasamy, Eimer and Shaffer, 2010: 796)
  • CLOTH MASKS MAY BE A PHYSICAL REMINDER NOT TO TOUCH THE FACE
    “…cloth masks and fabric materials covering the mouth and nose may serve as a reminder to not touch those areas with the hands serving to minimize contact transmission and reduce exposure to liquid splashes and droplets, although these premises would need to be confirmed experimentally. (Rengasamy, Eimer and Shaffer, 201: 796)

CONS

  • LIKELY MINIMUM RESPIRATORY PROTECTION
    “The use of fabric materials may provide only minimal levels of respiratory protection to a wearer against virus-size submicron aerosol particles (e.g. droplet nuclei). (Rengasamy, Eimer and Shaffer, 2010, p. 795) “Sandy and colleagues studied respirators, surgical and cloth masks and concluded that all three products provide respiratory protection to a degree, with respirators providing the maximum protection and homemade cloth masks the minimum.55” (Chughtai, Seale, and MacIntyre, 2013: 3)
  • LACK OF RESEARCH, UNKNOWN EFFECTIVENESS: MAY PROVIDE FALSE SENSE OF SECURITY
    “…household materials are not designed for respiratory protection and their use may provide a false sense of protection because their effectiveness against larger and <1000 nm size particles including viruses is not well understood.” (Rengasamy, Eimer and Shaffer, 2010: 790) “Our results highlight that there is currently [2013] no published research on the efficacy of cloth masks.” (Chughtai, Seale, and MacIntyre, 2013: 1) “Since the development of surgical masks and respirators, very little research has been conducted on cloth masks recently.” (Chughtai, Seale, and MacIntyre, 2013: 3) “The WHO discouraged masks use in the community setting during influenza A (H1N1) outbreaks due to lack of evidence, however, the option of use and reuse of various types of cloth masks is discussed. In case of cotton masks, WHO advises washing cloth masks with house hold detergent after use.72” (Chughtai, Seale, and MacIntyre, 2013: 4)
  • IMPROVISED FACE MASKS ARE COMPARABLE TO OTHER [NON N95] MASKS IN TERMS OF FILTRATION
    “The filtration efficiency of improvised fabric materials is comparable to some commonly used Federal Drug Agency-cleared surgical masks and unapproved dust masks…” (Rengasamy, Eimer and Shaffer, 2010: 795). “Thus, the penetration results obtained in the study indicate that the filtration performance of fabric materials is similar in some aspects to some surgical masks to reduce the transmission of infectious diseases. However, this study did not evaluate the fabric materials for protection against droplets and liquid splashes.” (Rengasamy, Eimer and Shaffer, 2010: 795)
    ==> Placed in “CON” since improvised masks are comparable to unapproved dust masks. Although a favorable comparison is made to FDA approved surgical masks, the unapproved dust mask comparison is not a “PRO.”

 

2B. Scholarly Findings and their Impact on Cloth Face Masks Making & Use 

SIZE OF INFLUENZA PARTICLES & TRAJECTORY

  • MOST VIRAL PATHOGEN DIAMETERS are under 1000 nm
    “…one study (Fabian et al., 2008) showed 87% of particles in exhaled breath of influenza-infected patients were under 1000 nm in diameter and the rest of the particles larger than that size” (Rengasamy, Eimer and Shaffer, 2010: 790)
    ==> GOAL: Find a material that a person may have at home that will intercept particles smaller than 1000 nm.
  • SHORT & LONG DISTANCES OF VIRAL MOVEMENT
    “… infected individuals produce smaller size particles (<1000 nm) that can travel long distances and larger size particles (~10000 nm) capable of reaching shorter distances.” (Rengasamy, Eimer and Shaffer, 2010: 790)
    ==> GOAL: Individuals wearing masks must still practice social distancing to address infection possibilities for short and long distances.

MASK DESIGN/FIT

  • BEST MASK EFFECTIVENESS OCCURS WHEN MASK IS DRY AND WELL-FITTING
    “The presence of moisture, distance traveled by the droplets and the design of mask were identified as other important factors related to the in-vitro filtration efficacy.” (Chughtai, Seale, and MacIntyre, 2013: 1) “Presence of moisture, distance traveled by the droplets and the design of mask were some other factors affecting the filtration capacity. In summary, the filtration capacity of wet masks has been reported as being lower compared to dry masks.58, 60 The distance traveled by the droplets is associated with the filtration capacity and filtration capacity is generally decreased by decreasing distance.31, 61” (Chughtai, Seale, and MacIntyre, 2013: 3)
    ==> Once the mask gets wet, its effectiveness decreases.
  • MASK SHOULD AIM TO CREATE SEAL ON FACE
    “Face seal leakage will further decrease the respiratory protection offered by fabric materials.” (Rengasamy, Eimer and Shaffer, 2010: 795-796) “…face seal leakage of aerosol particles was not measured, which is a critical component of respiratory protection.” (Rengasamy, Eimer and Shaffer, 2010: 796) “…only marginal respiratory protection can be expected for submicron particles taking into consideration face seal leakage.” (Rengasamy, Eimer and Shaffer, 2010: 796) “…the design of a mask is also important and some designs are more effective than others, particularly those with a tight seal around the face.40,54,61,62” (Chughtai, Seale, and MacIntyre, 2013: 3)
    ==> GOAL: Best to address leaks from masks and between mask and face since leaks influence effectiveness.

MASK MATERIALS

  • CLOTH STRUCTURE TO BE FINE, LIKELY COTTON & USED IN LAYERS
    “Generally, the filtration capacity improved when the number of threads increased in the gauze and the mesh become finer compared to course gauze with lower thread counts.31,40,57 Similarly, the number of layers was found to be directly proportional to the filtration capacity in most of the laboratory studies. In these studies, the filtration effectiveness significantly improved with increasing the number of layers in the mask.31,40,58,59” (Chughtai, Seale, and MacIntyre, 2013: 3) “In cases of non-availability of surgical masks, CDC recommends using cotton masks made from four or five layers of cotton cloth for infection control of viral hemorrhagic fevers in the African health care setting.71” (Chughtai, Seale, and MacIntyre, 2013: 4)
  • FIBRE CONTENT OF CLOTH MASKS: COTTON IS MOST CITED
    “In this [Chughtai, Seale, and MacIntyre research] setting, we refer to cloth masks as ‘reusable masks made of cloth or any other fabric, including cotton, gauze, silk or muslin’.” (Chughtai, Seale, and MacIntyre, 2013: 2)
    ==> In their description of “fabric,” the authors include both fibres (i.e. cotton, silk) and terms generally associated with weave structures (i.e. gauze, muslin). This leads to confusion in the article.
    ==> Vocabulary matters as, for instance, all muslins can technically be described as gauzes but not all gauzes can be muslins. Furthermore, all fabrics may be describes as cloths but not all cloths can be described as fabrics.

  • CLOTH WEAVE STRUCTURE
    “Certain types of cloth provides better protection than other; e.g. fine muslin (loosely-woven cotton fabric) was better than the [very loosely-woven cotton surgical] gauze,58 [very loosely-woven cotton surgical] gauze padded with [a filler of compressed] cotton were better than simple [very loosely-woven cotton surgical] gauze or paper masks [made of paper similar to paper toweling ]60 and towels were more effective than other fabrics.56 Cloths masks were generally found to be effective against large particles (>4 um),53 however some evidence exists against small particles as well.43 (Chughtai, Seale, and MacIntyre, 2013: 3)
    ==> Vocabulary is an issue in this quote for each of the research findings the authors are reporting on.

    • For “fine muslin (loosely-woven cotton fabric) was better than the gauze,58”:
      • When the authors use the word "GAUZE," we are not sure if they mean silk, linen or cotton gauze and how this differs from the "fine muslin" (also called loosely woven cotton fabric). In the document cited in note #58, we get a reference to “surgical gauze,” which is described as “non-medicated,” in “a very open weave,” “wide-meshed,” and “commonly used for dressings.” (Mason, 1919: 392) There is no mention of the fibre content but, in 1919, we can assume it is cotton.
      • As such, the word passage “gauze58,” should be prefaced by “very loosely-woven cotton surgical.”
    • For “gauze padded with cotton were better than simple gauze or paper masks60”:
      • In the document cited in note #60, no fibre content is used to describe "GAUZE." We can only ask assume that it is the same “very loosely woven cotton surgical” gauze.
      • In the document cited in note #60, the PAD OF COTTON is not defined as woven or non-woven. It is described as “filler of compressed cotton,” “layer of cotton,” “heavy cotton fillers.” (Mckhann, Steeger and Long, 1938: 596-598)
      • When the authors use the word "PAPER MASK," we don't know what kind of paper mask they are talking about. However, if we find the document referenced in endnote #60, the paper is described as “made of paper similar to paper toweling.” (Mckhann, Steeger and Long, 1938: 596, 598)
    • For “towels were more effective than other fabrics.56”:
      • When the authors use the word "TOWEL," we cannot know the fibre or weave structure. However, if we find the document referenced in endnote #56, the towel is described as a “bath towel,” “100% Cotton” and “80% Polyester 20% Nylon” with the “cotton towel model” showing “slightly higher resistance levels than the other fabric materials.” (Rengasamy, Eimer, and Shaffer, 2010: 789-798)
  • 1959 TESTS ON 3 TYPES OF COTTON MASKS FOUND EFFECTIVE: 4-LAYERS, 2-LAYERS WITH PAPER INSERT, [UNKNOWN LAYERS] WITH ADDITION OF CELLULOSE WADDING
    “In 1959, Shooter and colleagues evaluated three types of masks to prevent the spread of staphylococci from the wearer. They compared a four layer cotton mask, with a mask made from two layers of woven cambric with a piece of paper in between and a paper mask surrounded by cellulose wadding. All three masks were found effective in preventing spread of staphylococcal infection.52 (Chughtai, Seale, and MacIntyre, 2013: 3)
    ==> Size of bacterial particle is larger than a virus here (>1000 nm) but a different design, including non-woven inserts is interesting.
  • ENCAPSULATION MAY BE MORE EFFECTIVE
    “Low perceived effectiveness of the masks used during that [1918] pandemic was attributed to the poor quality of masks, inappropriate use of masks.40 In comparison, the rate of infection was very low amongst [Health Care Workers] who used masks made of a half-inch thick cotton pad enclosed by two layers gauze, during the Manchurian Epidemic in 1920–1921.41” (Chughtai, Seale, and MacIntyre, 2013: 2)
  • COTTON IN CALIFORNIA PANDEMIC INFLUENZA PLAN
    “…some regional pandemic influenza plans discuss the use of cloth masks in certain situations. For example; in California, Sonoma County Department of Health Services developed plan for pandemic influenza and recommended cotton masks in the event of a shortage of N95 respirators and surgical masks.51 (Chughtai, Seale, and MacIntyre, 2013: 2-3)
  • LACK OF REGULATION OF QUALITY AND NATURE OF CLOTH
    “Recently, the high demand for masks and the potential reliance on cloth masks during an influenza pandemic, was acknowledged by the Institute of Medicine (IOM) when preparing their report on the reusability of facemasks. The committee members did not advise against the use of cloth masks, however they recommended further research be undertaken on the use of cloth masks, including commonly used fabrics like T-shirts, handkerchiefs and scarves.25 One of the issues is that the quality and nature of cloth masks used around the world are varied and not subject to any regulation.” (Chughtai, Seale, and MacIntyre, 2013: 4)

 

2C. Bibliography of Works Cited in this Section

Chughtai, Abrar Ahmad, Holly Seale, and Chandini Raina MacIntyre. "Use of cloth masks in the practice of infection control—evidence and policy gaps." International Journal of Infection Control 9, no. 3 (2013). https://doi.org/10.3396/ijic.v9i3.11366

Mason, Leete, H. "Some Experiments on Masks." The Lancet 193, no. 4984 (1919): 392-393.

http://dx.doi.org/10.1016/S0140- 6736(01)49329-9

Mckhann, Charles F., Adelbert Steeger, and Arthur P. Long. "Hospital Infections: A Survey of the Problem." American Journal of Diseases of Children 55, no. 3 (1938): 579-599. doi:10.1001/archpedi.1938.01980090127015

Rengasamy, Samy, Benjamin Eimer, and Ronald E. Shaffer. "Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles." The Annals of Occupational Hygiene 54, no. 7 (2010): 789-798. https://doi.org/10.1093/annhyg/meq044