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Cloth face mask
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<h2 id="usage">Usage</h2> <p class="note">See also: <a href="/facts/Face_masks_during_the_COVID-19_pandemic/u7qwlDwJ">Face masks during the COVID-19 pandemic</a></p> <p>Prior to the <a href="/facts/COVID-19_pandemic/0xTsh7Ut">COVID-19 pandemic</a>, reusable cloth face masks were predominantly used by healthcare workers, and in the community, in developing countries and in Asia. Cloth face masks contrast with <a href="/facts/Surgical_mask/azNpaTV3">surgical masks</a> and <a href="/facts/Respirator/rYFJThhR">respirators</a> such as <a href="/facts/N95_mask/bGgNSnNF">N95 masks</a>, which are made of <a href="/facts/Nonwoven_fabric/XeFJRS0B">nonwoven fabric</a> and contain a layer or layers formed through a <a href="/facts/Melt_blowing/BxFY5Y1S">melt blowing</a> process. Melt-blown materials have a fine, random, structure, which leads to excellent filtration properties. Respirators are regulated for their effectiveness based upon filtration efficiency of sub-micron <a href="/facts/NaCl/MWcXl3Mb">sodium chloride</a> particles (count median diameter 0.075 ± 0.020 μm; mass median diameter 0.26 μm),<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> along with other criteria such as outer splash/spray protection, inner splash/spray absorption, contaminant accumulation and shedding, breathability (or pressure drop across the mask), and inflammability.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Like surgical masks, and unlike respirators, cloth face masks do not provide a seal around the face, and prior to the 2019 COVID-19 outbreak were generally not authorized by institutions for protection from diseases recognized as airborne (e.g., tuberculosis).<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>In healthcare settings, they are used on sick patients as <a href="/facts/Source_control_(respiratory_disease)/set7gla4">source control</a> to reduce disease transmission through <a href="/facts/Respiratory_droplet/oMugYAEa">respiratory droplets</a> and respiratory aerosols and by healthcare workers when surgical masks and respirators are unavailable. Cloth face masks are only recommended for use by healthcare workers as a last resort if supplies of surgical masks and respirators are exhausted.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> They are also used by the general public in household and community settings to reduce the risks of both infectious diseases and <a href="/facts/Particulates/RleGr5E6">particulate</a> <a href="/facts/Air_pollution/zmk9Dy7S">air pollution</a> and to contain the wearer's exhaled virus-laden droplets and aerosols.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p><p>Several types of cloth face masks are available commercially, especially in Asia.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> Homemade masks can also be improvised using <a href="/facts/Bandana/XeCIkK5G">bandanas</a>,<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> <a href="/facts/T-shirt/qj59PYsF">T-shirts</a>,<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> <a href="/facts/Handkerchief/STrIcnWg">handkerchiefs</a>,<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> <a href="/facts/Scarf/2zWvMKFS">scarves</a>,<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> or <a href="/facts/Towel/chqDrhN0">towels</a>.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> Depending on the design and materials, reusable cloth masks with incorporated filters can block particles as well as surgical masks.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> </p> <h2 id="recommendations">Recommendations</h2> <p>The <a href="/facts/World_Health_Organization/YNN3bgug">World Health Organization</a> (WHO) continues to recommend that masks be used as part of a comprehensive strategy of measures to suppress transmission and save lives; the use of a mask alone is not sufficient to provide an adequate level of protection against COVID-19.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> The US <a href="/facts/Center_for_Disease_Control/NmoJNDV5">Center for Disease Control</a>, along with <a href="/facts/Johns_Hopkins_University_School_of_Medicine/Mh6EHzKP">Johns Hopkins University School of Medicine</a>, <a href="/facts/The_Mayo_Clinic/QQbLLJza">The Mayo Clinic</a>, and <a href="/facts/Cleveland_Clinic/vqB0tyyF">Cleveland Clinic</a> all concur with this recommendation.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> The <a href="/facts/World_Health_Organization/YNN3bgug">World Health Organization</a> also recommended that those aged over 60 years old or with underlying health risks require more protection and should wear medical masks in areas where there is community transmission.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p><p>The <a href="/facts/World_Health_Organization/YNN3bgug">World Health Organization</a> recommends using masks with at least three layers of different materials. Two <a href="/facts/Spunbond/XeFJRS0B">spunbond</a> <a href="/facts/Polypropylene/HM9PvoCz">polypropylene</a> layers offer useful increases in filtration with acceptable breathability.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a><a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> When producing cloth face masks, two parameters should be considered: filtration efficiency of the material and breathability. The filter quality factor known as "Q" is commonly used as an integrated filter quality indicator. It is a function of filtration efficiency and breathability, with higher values indicating better performance. Experts recommend Q-factor of three or higher.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> The usefulness of this ratio in selecting materials for masks has not, to our knowledge, been demonstrated. </p><p>A peer-reviewed summary<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> of the filtration properties of cloth and cloth masks concluded that, pending further research, evidence is strongest for 2 to 4 layers of plain weave cotton or flannel, at least 100 <a href="/facts/Thread_count/HylEIRGM">thread count</a>. A plain-language summary of this review is available.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> </p> Comparison of materials for fabric masks<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a><table><tbody><tr><th>Material (source)</th><th>Structure</th><th>Initial Filtration Efficiency (%)</th><th>Initial Pressure drop (Pa)</th><th>Filter quality factor, Q (kPa−1)</th></tr><tr><td><a href="/facts/Polypropylene/HM9PvoCz">Polypropylene</a> (interfacing material)</td><td><a href="/facts/Spunbond/XeFJRS0B">spunbond</a></td><td>6</td><td>1.6</td><td>16.9</td></tr><tr><td>Cotton (sweater)</td><td>knit</td><td>26</td><td>17</td><td>7.6</td></tr><tr><td>Cotton (T-shirt)</td><td>knit</td><td>21</td><td>14.5</td><td>7.4</td></tr><tr><td><a href="/facts/Polyester/Ivp9CHpl">Polyester</a> (toddler wrap)</td><td>knit</td><td>17</td><td>12.3</td><td>6.8</td></tr><tr><td>Cotton (T-shirt)</td><td>woven</td><td>5</td><td>4.5</td><td>5.4</td></tr><tr><td><a href="/facts/Cellulose/wYPafTU0">Cellulose</a> (tissue paper)</td><td>bonded</td><td>20</td><td>19</td><td>5.1</td></tr><tr><td>Cellulose (paper towel)</td><td>bonded</td><td>10</td><td>11</td><td>4.3</td></tr><tr><td>Silk (napkin)</td><td>woven</td><td>4</td><td>7.3</td><td>2.8</td></tr><tr><td>Cotton (handkerchief)</td><td>woven</td><td>1.1</td><td>9.8</td><td>0.48</td></tr><tr><td>Cotton, <a href="/facts/Gauze/Fa3bXGf2">gauze</a></td><td>woven</td><td>0.7</td><td>6.5</td><td>0.47</td></tr><tr><td><a href="/facts/Nylon/hBvG9bCw">Nylon</a> (exercise pants)</td><td>woven</td><td>23</td><td>244</td><td>0.4</td></tr></tbody></table> <h2 id="efficiency">Efficiency</h2> <p>Cloth face masks can be used for <a href="/facts/Source_control_(respiratory_disease)/set7gla4">source control</a> to reduce disease transmission arising from the wearer's <a href="/facts/Respiratory_droplet/oMugYAEa">respiratory droplets</a> and respiratory aerosols, and also to reduce risk for the wearer by filtering incoming aerosols,<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> thereby reducing disease transmission,<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> but are not considered <a href="/facts/Personal_protective_equipment/DF3oEH6B">personal protective equipment</a> for the wearer in regulated or health-and-safety contexts<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a><a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a><a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> Filtration efficiency of the material is typically low compared with non-woven materials used in surgical masks and respirators.<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a><a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> However, a well-designed cloth mask may fit very well, with little edge leak. In contrast, surgical mask material is an excellent filter, but surgical masks typically fit poorly, with visible gaps and large edge leaks. This explains why cloth masks (less good filter, good fit) and surgical masks (good filter, less good fit) perform similarly in tests of protection of the wearer from aerosol-sized particles.<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a><a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> </p><p>As of 2015, there had been no <a href="/facts/Randomized_controlled_trial/LG9lkyVx">randomized clinical trials</a> or guidance on the use of reusable cloth face masks.<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a><a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> Most research had been performed in the early 20th century, before disposable surgical masks became prevalent. One 2010 study found that 40–90% of particles in the 20–1000 nm range penetrated a cloth mask and other fabric materials.<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a> The performance of cloth face masks varies greatly with the shape, fit, and type of fabric,<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a> as well as the fabric fineness and number of layers.<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a> As of 2006, no cloth face masks had been cleared by the U.S. <a href="/facts/Food_and_Drug_Administration/rCEnh9WB">Food and Drug Administration</a> for use as surgical masks.<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a> A Vietnamese study of healthcare workers compared influenza-like illness outcome among those wearing cloth masks versus medical masks.<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a> They concluded that cloth masks were ineffective at preventing transmission in high-risk clinical settings. Although discouraged in clinical settings, cloth masks may still serve a useful role in reducing disease transmission in public settings according to a systematic review.<a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a><a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a> </p><p>One role of masks worn by the general public is to "stop those who are already infected broadcasting the virus into the air around them" or source control.<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a> This is of particular importance with the <a href="/facts/COVID-19_pandemic/0xTsh7Ut">COVID-19 pandemic</a>, as transmission from people who are asymptomatic is a key feature of its rapid spread.<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a> For example, of the people on board the <a href="/facts/COVID-19_pandemic_on_Diamond_Princess/2lJGScyP">Diamond Princess cruise ship</a>, 634 people were found to be infected—52% had no symptoms at the time of testing, including 18% who never developed symptoms.<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a> Best practice is to implement multiple prevention techniques to reduce risk, for example, increasing the proportion of outside air used in ventilation, filtration systems built into HVAC, stand-alone filtration systems such as HEPA filters and <a href="/facts/Corsi%25E2%2580%2593Rosenthal_Box/9085EgQw">Corsi-Rosenthal boxes</a>, avoiding crowded spaces, and practicing staying home while sick and for the period of probable infectiousness following illness.<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a> </p><p>Compared with bacteria recovery from unmasked volunteers, a mask made of muslin and flannel reduced bacteria recovered on agar sedimentation plates by 99%, total airborne microorganisms by 99%, and bacteria recovered from aerosols (< 4 μm) by 88% to 99%.<a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> In 1975, 4 medical masks and 1 commercially produced reusable mask made of 4 layers of cotton muslin were compared. Filtration efficiency, assessed by bacterial counts, was 96% to 99% for the medical masks and 99% for the cloth mask; for aerosols (< 3.3 μm), it was 72% to 89% and 89%, respectively.<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a> </p><p>An experiment carried out in 2013 by Public Health England, that country's health-protection agency, found that a commercially made surgical mask filtered 90% of virus particles from the air coughed out by participants, a vacuum cleaner bag filtered out 86%, a tea towel blocked 72% and a cotton t-shirt 51%—though fitting any DIY mask properly and ensuring a good seal around the mouth and nose is crucial.<a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a><a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a> The use of common fabrics in making face masks has been tested.<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a><a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a><a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a><a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a> Filter efficiency can be improved with multiple layers, but it is important also to consider breathability. Cotton is the most commonly used material, and filter efficiencies can reach > 80% for particles <. 300 nm with fabric combinations such as cotton-silk, cotton-chiffon, or cotton-flannel, though these filtration efficiencies are not directly comparable with the reported properties of surgical masks and respirators, because of the non-standard methods used in this study, conducted in the early months of the Covid-19 pandemic.<a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a> The WHO recommended that cloth masks should have three layers with a hydrophilic inner layer (e.g., cotton) to absorb moisture from the wearer's breathing, a filter layer, ideally spunbond polypropylene,<a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a> and a hydrophobic outer layers (e.g., polyester).<a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a> The benfits of a hydrophobic outer layer have not, to our knowledge, been demonstrated, and may be a throw-back to the idea of protection from droplets, which is now recognized as not the dominant mode of transmission.<a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a><a class="footnote-ref" id="fnref:70" href="#fn:70"><sup>70</sup></a><a class="footnote-ref" id="fnref:71" href="#fn:71"><sup>71</sup></a> Masks should be cleaned after each use. They can either be laundered or hand-washed in soapy hot water and dried with high heat.<a class="footnote-ref" id="fnref:72" href="#fn:72"><sup>72</sup></a> </p> <h2 id="history">History</h2> <p>In Roman times, <a href="/facts/Pliny_the_Elder/grx67ghR">Pliny the Elder</a> recommended that miners use animal bladders to protect against inhaling lead oxides. Some followers of <a href="/facts/Jainism/h0glxhjH">Jainism</a>, which originated in India around 500 B.C.E, wear cloth masks to avoid accidentally inhaling insects as part of practicing <a href="/facts/Ahimsa/gV8J0KQI">ahimsa</a>.<a class="footnote-ref" id="fnref:73" href="#fn:73"><sup>73</sup></a><a class="footnote-ref" id="fnref:74" href="#fn:74"><sup>74</sup></a><a class="footnote-ref" id="fnref:75" href="#fn:75"><sup>75</sup></a> In the 16th century, <a href="/facts/Leonardo_da_Vinci/E83tcPl2">Leonardo da Vinci</a> advised the use of a wet woven cloth to protect against toxic agents[<i>which?</i>] of chemical warfare.<a class="footnote-ref" id="fnref:76" href="#fn:76"><sup>76</sup></a> In the early modern period, the <a href="/facts/Plague_doctor_costume/tqI3h3FW">plague-doctor costume</a> included a beaked face-mask worn to protect the wearer from infectious "<a href="/facts/Miasma_theory/gykpNzz4">miasma</a>". </p><p>Conventional <a href="/facts/Cowboy/JhyeFWqY">cowboy</a> attire in the <a href="/facts/American_West/uY9UGAus">American West</a> often included a <a href="/facts/Bandanna/XeCIkK5G">bandanna</a>, which could protect the face from blown dust and also potentially doubled as a means of obscuring identity.<a class="footnote-ref" id="fnref:77" href="#fn:77"><sup>77</sup></a> </p><p>In 1890 <a href="/facts/William_Stewart_Halsted/Sjnr0Abf">William Stewart Halsted</a> pioneered the use of rubber gloves and surgical face masks, although some European surgeons such as <a href="/facts/Paul_Berger_(physician)/xBccy1uN">Paul Berger</a> and <a href="/facts/Jan_Mikulicz-Radecki/NHIkJrGb">Jan Mikulicz-Radecki</a> had worn cotton gloves and masks earlier. These masks became commonplace after World War I and the influenza pandemic of 1918.<a class="footnote-ref" id="fnref:78" href="#fn:78"><sup>78</sup></a><a class="footnote-ref" id="fnref:79" href="#fn:79"><sup>79</sup></a> Cloth face masks were promoted by <a href="/facts/Wu_Lien-teh/160DpWYf">Wu Lien-teh</a> in the 1910–11 <a href="/facts/Manchurian_plague/joGkPQHK">Manchurian pneumonic plague outbreak</a>, although Western medics doubted their efficacy in preventing the spread of disease.<a class="footnote-ref" id="fnref:80" href="#fn:80"><sup>80</sup></a> </p><p>Cloth masks were largely supplanted by modern <a href="/facts/Surgical_mask/azNpaTV3">surgical masks</a> made of <a href="/facts/Nonwoven_fabric/XeFJRS0B">nonwoven fabric</a> in the 1960s.<a class="footnote-ref" id="fnref:81" href="#fn:81"><sup>81</sup></a><a class="footnote-ref" id="fnref:82" href="#fn:82"><sup>82</sup></a> Peer reveiwed evidence supporting their equivalence appears to be lacking. The use of cloth masks continued in developing countries.<a class="footnote-ref" id="fnref:83" href="#fn:83"><sup>83</sup></a> They were used in Asia during the <a href="/facts/2002%25E2%2580%25932004_SARS_outbreak/3k6cvrqL">2002–2004 SARS outbreak</a>, and in West Africa during the <a href="/facts/Western_African_Ebola_virus_epidemic/8Tr58t6q">2013–2016 Ebola epidemic</a>.<a class="footnote-ref" id="fnref:84" href="#fn:84"><sup>84</sup></a> Compared with bacteria recovery from unmasked volunteers, a mask made of muslin and flannel reduced bacteria recovered on agar sedimentation plates by 99%, total airborne microorganisms by 99%, and bacteria recovered from aerosols (<4 μm) by 88% to 99%.<a class="footnote-ref" id="fnref:85" href="#fn:85"><sup>85</sup></a> In 1975, 4 medical masks and 1 commercially produced reusable mask made of 4 layers of cotton muslin were compared. Filtration efficiency, assessed by bacterial counts, was 96% to 99% for the medical masks and 99% for the cloth mask; for aerosols (<3.3 μm), it was 72% to 89% and 89%, respectively.<a class="footnote-ref" id="fnref:86" href="#fn:86"><sup>86</sup></a> </p> <h3>COVID-19 pandemic</h3> <p class="note">Main article: <a href="/facts/Face_masks_during_the_COVID-19_pandemic/u7qwlDwJ">Face masks during the COVID-19 pandemic</a></p> <p>In the early years of the <a href="/facts/COVID-19_pandemic/0xTsh7Ut">COVID-19 pandemic</a>, most countries recommended the use of cloth masks to reduce the spread of the virus.<a class="footnote-ref" id="fnref:87" href="#fn:87"><sup>87</sup></a> </p><p>On June 5, 2020, WHO changed its advice on face masks, recommending that the general public should wear fabric masks where widespread COVID-19 transmission exists and physical distancing is not possible (for example, "on public transport, in shops or in other confined or crowded environments").<a class="footnote-ref" id="fnref:88" href="#fn:88"><sup>88</sup></a><a class="footnote-ref" id="fnref:89" href="#fn:89"><sup>89</sup></a> The WHO continues to recommend their use: 'Masks should be used as part of a comprehensive strategy of measures to suppress transmission and save lives; the use of a mask alone is not sufficient to provide an adequate level of protection against COVID-19.'<a class="footnote-ref" id="fnref:90" href="#fn:90"><sup>90</sup></a> The CDC also continues to recommend masking: 'Wearing a mask is an additional prevention strategy that you can choose to further protect yourself and others.'<a class="footnote-ref" id="fnref:91" href="#fn:91"><sup>91</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/N95/CHL8619Q">N95</a> - a mask designed to stop the spread of airborne disease, e.g., <a href="/facts/Tuberculosis/ggPyovAl">tuberculosis</a> and for use in industrial settings</li> <li><a href="/facts/Nose_filter/2DhyoURm">Nose filter</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html/">CDC Mask Guidance – Help Slow the Spread</a></li> <li><a href="https://www.youtube.com/watch?v=r7ywjj6mJGk">NPR: 3 Tips for Safer Face Masks</a> (video on <a href="/facts/YouTube/db276jst">YouTube</a>)</li> <li><a href="https://www.youtube.com/watch?v=gaka1vqYFNs">Mayo Clinic expert on nonmedical mask use to prevent public transmission</a> (video on <a href="/facts/YouTube/db276jst">YouTube</a>)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Mask Hierarchy". Mask Evidence. Retrieved February 18, 2025. <a href="https://maskevidence.org/mask-types" target="_blank">https://maskevidence.org/mask-types</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Andrejko, Kristin L. (2022). "Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021". MMWR. Morbidity and Mortality Weekly Report. 71 (6): 212–216. doi:10.15585/mmwr.mm7106e1. ISSN 0149-2195. PMC 8830622. PMID 35143470. <a href="https://www.cdc.gov/mmwr/volumes/71/wr/mm7106e1.htm?s_cid=mm7106e1_w" target="_blank">https://www.cdc.gov/mmwr/volumes/71/wr/mm7106e1.htm?s_cid=mm7106e1_w</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings". U.S. Centers for Disease Control and Prevention. May 18, 2020. Retrieved May 21, 2020. <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control-recommendations.html" target="_blank">https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control-recommendations.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"COMMENTARY: Wear a respirator, not a cloth or surgical mask, to protect against respiratory viruses | CIDRAP". www.cidrap.umn.edu. February 23, 2023. Retrieved February 18, 2025. <a href="https://www.cidrap.umn.edu/covid-19/commentary-wear-respirator-not-cloth-or-surgical-mask-protect-against-respiratory-viruses" target="_blank">https://www.cidrap.umn.edu/covid-19/commentary-wear-respirator-not-cloth-or-surgical-mask-protect-against-respiratory-viruses</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>MacIntyre, C. R.; Chughtai, A. A. (April 9, 2015). "Facemasks for the prevention of infection in healthcare and community settings" (PDF). 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