Interesting Study of Cloth Face Masks

[Kitiger, RN]

"Thus, hydrophilicity or soaking ability of home fabrics do not prevent them from blocking droplets. They provide an alternative mechanism of droplet blocking, in contrast to the water repellant hydrophobic medical masks."

"Most home fabrics are hydrophilic (water soaking), compared to highly hydrophobic medical masks. This does not prevent home fabrics from blocking droplets. In contrast to medical masks, they soak and hold the droplets. This holding ability may offer additional untapped and under-studied advantage of home-made masks."

Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks

Abstract

The emergence of a pandemic affecting the respiratory system can result in a significant demand for face masks. This includes the use of cloth masks by large sections of the public, as can be seen during the current global spread of COVID-19. However, there is limited knowledge available on the performance of various commonly available fabrics used in cloth masks. Importantly, there is a need to evaluate filtration efficiencies as a function of aerosol particulate sizes in the 10 nm to 10 μm range, which is particularly relevant for respiratory virus transmission. We have carried out these studies for several common fabrics including cotton, silk, chiffon, flannel, various synthetics, and their combinations. Although the filtration efficiencies for various fabrics when a single layer was used ranged from 5 to 80% and 5 to 95% for particle sizes of <300 nm and >300 nm, respectively, the efficiencies improved when multiple layers were used and when using a specific combination of different fabrics. Filtration efficiencies of the hybrids (such as cotton-silk, cotton-chiffon, cotton-flannel) was >80% (for particles <300 nm) and >90% (for particles >300 nm). We speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration. Cotton, the most widely used material for cloth masks performs better at higher weave densities (I.e., thread count) and can make a significant difference in filtration efficiencies. Our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60% decrease in the filtration efficiency, implying the need for future cloth mask design studies to take into account issues of "fit" and leakage, while allowing the exhaled air to vent efficiently. Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.

Keywords: COVID-19; SARS-CoV-2; aerosols; cloth masks; face masks; personal protection; respiratory protection.

https://pubmed.ncbi.nlm.nih.gov/32329337/

[NurseBlaq]

Interesting. I've been waiting on a study like this because I haven't been wearing cloth masks due to not knowing how effective they really are and being high risk. I've seen some mask patterns with the ability to add a filter in them and wondered if that adds an additional protection. Hope they do a study with that next.

[Wuzzie]

37 minutes ago, NurseBlaq said:

Interesting. I've been waiting on a study like this because I haven't been wearing cloth masks due to not knowing how effective they really are and being high risk.

There were earlier studies that also indicated at least some efficacy in wearing cloth masks. I am high risk and understand full well that my mask primarily protects others but I think it makes sense that it also protects me, at least to some degree, more than no mask at all.

[NurseBlaq]

12 minutes ago, Wuzzie said:

There were earlier studies that also indicated at least some efficacy in wearing cloth masks. I am high risk and understand full well that my mask primarily protects others but I think it makes sense that it also protects me, at least to some degree, more than no mask at all.

Agreed. I've been wearing surgical masks. I didn't want to wear cloth masks until I had more info on the efficacy. I must have missed those studies. Do you have links or can point me in the right direction?

[Kitiger, RN]

21 minutes ago, NurseBlaq said:

Agreed. I've been wearing surgical masks. I didn't want to wear cloth masks until I had more info on the efficacy. I must have missed those studies. Do you have links or can point me in the right direction?

https://pubmed.ncbi.nlm.nih.gov/32329337/

[NurseBlaq]

Thanks. Found this in one of the similar articles

Quote

Only three studies directly compared the protective value of surgical masks with N95 masks. The majority of laboratory studies identified both mask types as having a range of filtration efficiency, yet N95 masks afford superior protection against particles of a similar size to influenza.

https://pubmed.ncbi.nlm.nih.gov/20095070/

[Wuzzie]

Unfortunately the bulk of studies are looking at it from a "protect the wearer" or health care worker standpoint which, as we all know, isn't the point. It just makes sense that any sort of barrier is going to help decrease the amount of droplets spewed out otherwise why do we bother covering our mouth at all when we sneeze or cough? I still put my masked face into my elbow when I do either of those things so double protection.

Also one of those studies cultured both sides of the masks and, although it seems they were trying to disprove the benefits of cloth masks, they reported no Covid on the inside (ostensibly to say "look it didn't stop it") but Covid on the outside. Well, it seems to me that Covid on the outside of my mask is better than Covid on my face. YMMV

[NurseBlaq]

11 minutes ago, Wuzzie said:

Unfortunately the bulk of studies are looking at it from a "protect the wearer" or health care worker standpoint which, as we all know, isn't the point. It just makes sense that any sort of barrier is going to help decrease the amount of droplets spewed out otherwise why do we bother covering our mouth at all when we sneeze or cough? I still put my masked face into my elbow when I do either of those things so double protection.

Also one of those studies cultured both sides of the masks and, although it seems they were trying to disprove the benefits of cloth masks, they reported no Covid on the inside (ostensibly to say "look it didn't stop it") but Covid on the outside. Well, it seems to me that Covid on the outside of my mask is better than Covid on my face. YMMV

That part!

[Littleblackdog, ADN, BSN, RN]

Thank you for posting this; found it very helpful indeed and certainly interesting. I printed out a copy to keep to reference now and again. Good to read this, Thanks again!