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ASTM Base Efficiency Requirement can be Combined With More Efficient Masks to Greatly Reduce COVID Transmission

Are Nanofiber Media Masks More Comfortable?

International Filtration News Insights

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ASTM Base Efficiency Requirement can be Combined With More Efficient Masks to Greatly Reduce COVID Transmission

There are presently many masks being worn where even with a perfect fit the efficiency will be well less than 20%. So an ASTM standard which would result in all masks being somewhat effective will be a contribution. With CATER Mask Decisions we hope to guide a majority of purchasers to purchase much more efficient masks.

At the very least we should be able to achieve a distribution where 20% are wearing masks which are 80% efficient or greater and 10% are wearing very efficient masks. The masks are part of the swiss cheese defense program. The fewer holes in the mask layer, the less need there is to eliminate holes in the ventilation layer or in quarantine.

The ASTM working group struggled to find compromise on inward leakage testing. There is no consideration of quality control. So the reality in terms of virus protection ranges roughly from 5 to 80%.

It is therefore important that the ASTM standard be supplemented by evaluation systems which provide net effectiveness even if it is a range such as shown in the following chart.

Effectiveness Rating %
	Minimum	Maximum
Level 1	0	10
Level 2	10	30
Level 3	50	70
Level 4	70	95

This effectiveness rating could be net efficiency as calculated in the following example.

Mask	Efficiency %	Unfiltered %	Defects	Net Efficiency %
CATER 99	98-99	-2-8	0-1	89-97
CATER 95	92-97	-2-8	0-1	83-95
CATER 93	90-95	-2-8	0-1	82-93
Cloth	50-60	-30-50	5-10	15-37
Surgical	92-97	-25-40	0-1	40-72

Obtaining agreement of mask standards is difficult considering the revenues for inefficient masks are many billions of dollars per year. So the fact that ASTM has been working with CDC and can probably have a consensus on a minimum 20% efficiency mask is significant. Also the clarification of methods to test efficiency is also an important part of the effort

This week the group received a request to vote on Ballot Action: Working Draft #7, Standard Specification for Barrier Face Coverings

This draft incorporates recommended changes from the work group provided on Draft #6. A number of specific changes have been made in response to recent teleconferences to find potential areas of consensus. Many of these comments are substantial particularly as related to leakage assessment, labeling, and conformity assessment.

Note 4 – The leakage assessment represents the total inward leakage likely to occur during wear. Whether measured quantitatively or assessed qualitatively, the leakage assessment does not represent the likely outward leakage of particles generated by the wearer. Thus, no claims may be made with respect to the degree of source control offering by the barrier face covering based on the leakage assessment.

Note 5 – Leakage assessment, if measured quantitatively on a barrier face covering that rests closely on the face and thus has minimal inward volume, may not be representative of true inward leakage.

4.1.3 Sub-micron particulate filtration efficiency and air flow resistance do not account for the leakage of air around the perimeter of the barrier face covering. A leakage assessment using a design analysis of the product is required to assess the ability of the barrier face covering design to minimize inward leakage and provide appropriate coverage for a range of wearer faces of different dimensions. The design analysis can be conducted by the manufacturer in a number of different ways. The standard also permits supplemental the use of quantitative information obtained from a modified form of Test Method F3407 using test subjects. This test yields a reportable ratio of outside particulate concentration to the concentration of particles in the wearer’s breathing zone. Thus, a leakage ratio of 1.0 indicates the outside and inside environments are equal and that particulate flow through gaps in the barrier face covering (in addition to any particulate that pass through the filtration materials of the product

5.4.1 The leakage assessment shall be reported by the manufacturer through a product design analysis self-declaration.

5.4.2 The required self-declaration shall report that the product minimizes leakage around the edges or other areas of the product based upon an analysis of the product design. This statement can be included on any self-declaration required as part of Guide F3050, under Section 12 of this specification.

5.4.2.1 The manufacturer is permitted to conduct quantitative testing to supplement its product design analysis self-declaration. When used, the leakage ratio shall be evaluated using Test Method F3407, with the modifications specified in 8.3.

5.4.3 Where barrier face coverings are reusable and intended for laundering or cleaning, the product design analysis shall be applied to barrier face coverings both in a new condition and after the maximum of laundering or cleaning cycles as specified by the manufacturer according to the manufacturer care instructions.

Note 13 – Examples of means to accomplish a leakage assessment could include dimensional analysis, computer modeling, placement of barrier face coverings on standardized head or head-torso forms and judging their respective areas of coverage and conformity to the head or head-torso form face showing conformance to the fit and sizing characterizations of AATCC M14-2020, or performing a quantitative analysis.[1]

This ASTM standard is a sign of progress. It alerts buyers that all masks are not equal. Suppliers of 95% efficient masks with less than 8% inward leakage can use this standard as a base and provide evidence as to why their product achieves their claims,

Are Nanofiber Media Masks More Comfortable?

Revolution fibres make a case that not only do nanofibers have efficiency and breathability advantages they are also more comfortable.

Nanofibers are incredibly small, synthetic fibers – each measuring one thousand times thinner than a human hair. Nanofibers form complex strength through spiderweb-like structures, which have an advantage over conventional or even natural fibers due to their extraordinarily large surface area and tiny pore size. This combination creates maximum air flow and particle capture – significantly more than other synthetic or natural filters, achieving greater efficiency down to PM0.3 microns.

This image helps us visualize the size of a nanofiber when compared to both hair and a speck of pollen:

Its small size provides an array of benefits when utilized in face mask technology – including advanced protection and better comfort.

Featuring a weaving design closely packed together so microscopically that we are unable to see them with the human eye, nanofibers craft a small pore size and high surface-to-volume ratio. This means the surface area and pores of a face mask with nanofiber technology will not allow cells to pass through to reach the wearer. Simply, due to the unique and tough threading of the nanofibers, everyday dangers such as pollution, viruses, bacteria and more will be unable to cross the threshold of the mask, thereby enhancing protection from the outside world. Not even water or liquid can penetrate the surface, which is why it is such an essential component of any truly effective face mask.

Additionally, this works two ways, as a mask is not only a protector of the individual wearing the mask, but it also serves to halt the spread of germs as well. When you’re sick, you should have a mask on – especially if there are other people in your household or if you are traveling out to an appointment with a doctor. Nanofibers block larger cells from escaping the mask, which helps to ensure less spread of any unpleasant or harmful ailment to unsuspecting passersby or loved ones.

While many are aware of the advanced protection that nanofibers provide in face mask technology, what may come as a surprise is that this material is also significantly more comfortable than other fibers. The complexity of the microscopic hair-like design makes the mask lightweight and, therefore, extremely breathable. It’s not simply a cloth over your face – it’s a material that works with your body to trap cells out but allow air to flow in, so you don’t feel cramped or suffocated. This also allows for better temperature regulation. More airflow means less of a “humid” feeling, as if the mask were a part of your face rather than your face feeling as if it’s sweating into the mask. The light, soft and airy material of nanofibers ensures both short-term and long-term wear is much more comfortable.

Overall, nanofibers have revolutionized the way we keep people safe – with transformational applications in healthcare advancements such as tissue engineering, wound dressings, face masks and more.

International Filtration News has lots of good information relative to masks We work closely with Matt Migliore who is the editor. He just wrote an article on nanofibers which is quite relevant. Here are some excerpts.

According to Dr. Vijayakumar, to truly deliver on the benefits of increased efficiency and decreased resistance in the filter, nanofibers need to be in the ~100nm size range.

NXTNANO’s HYPR spinning production process is capable of scaling to produce approximately 150 million square meters of Level 1 mask material per year, according to McDowell. Described as a derivative of electrospinning, the HYPR spinning process allows NXTNANO to produce more and finer fiber, more consistently, and with better bonding than other nanofiber material options on the market. It also permits flexibility to spin multiple polymers simultaneously. “All of the general issues you would see with electrospinning we think we’ve pretty well solved; for throughput, controllability, and uptime,” said McDowell.

There is an important article by Adrian Wilson titled Facemask materials, surface treatments, intelligent sensors & carbon nanotubes. Here is an excerpt.

NWI executive director Benham Pourdeyhimi explained that the new media development arose from reactivated work on microfibrillation, which was initially undertaken for the filtration industry.

N95 efficiency can be achieved with just two layers of the new spunbond fabric. A combination of one spunbond layer and a meltblown layer can further achieve N99 efficiency.

The media also requires no electrostatic charging, which has been another bottleneck in the production of facemasks this year, and, because the materials are strong – unlike traditional meltblown materials – they can also be cut and sewn by traditional techniques. Further, they have the potential to be reused a number of times after cleaning.