Virus Remains Live after Travel of Sixteen Feet

Small Mask Gaps Result in Big Efficiency Losses

VPM Research Studies Vapor Deposition on Nanofibers

August 20, 2020 - Mask Selection Webinar  Now Posted on YouTube

Mask Webinar Today Probed Major Issues in Mask Selection

Vogmask has Both Valved and Non-Valved Masks

Abhishek Saha of UCSD Focuses on Potential for Aerosol Generation from Droplets on Masks

Comparison of Meltblowns and Nanofiber Mask Cleaning Impacts

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Virus Remains Live after Travel of Sixteen Feet

A research team at the University of Florida succeeded in isolating live virus from aerosols collected at a distance of seven to 16 feet from patients hospitalized with Covid-19 — farther than the six feet recommended in social distancing guidelines.

The NY Times reports that in the new study, researchers devised a sampler that uses pure water vapor to enlarge the aerosols enough that they can be collected easily from the air. Rather than leave these aerosols sitting, the equipment immediately transfers them into a liquid rich with salts, sugar and protein, which preserves the pathogen.

“I’m impressed,” said Robyn Schofield, an atmospheric chemist at Melbourne University in Australia, who measures aerosols over the ocean. “It’s a very clever measurement technique.”

As editor of the journal Atmospheric Measurement Techniques, Dr. Schofield is familiar with the options available, but said she had not seen any that could match the new one.

The researchers had previously used this method to sample air from hospital rooms. But in those attempts, other floating respiratory viruses grew faster, making it difficult to isolate the coronavirus.

This time, the team collected air samples from a room in a ward dedicated to Covid-19 patients at the University of Florida Health Shands Hospital. Neither patient in the room was subject to medical procedures known to generate aerosols, which the W.H.O. and others have contended are the primary source of airborne virus in a hospital setting.

The team used two samplers, one about seven feet from the patients and the other about 16 feet from them. The scientists were able to collect virus at both distances and then to show that the virus they had plucked from the air could infect cells in a lab dish.

The genome sequence of the isolated virus was identical to that from a swab of a newly admitted symptomatic patient in the room.

The room had six air changes per hour and was fitted with efficient filters, ultraviolet irradiation and other safety measures to inactivate the virus before the air was reintroduced into the room.

That may explain why the researchers found only 74 virus particles per liter of air, said John Lednicky, the team’s lead virologist at the University of Florida. Indoor spaces without good ventilation — such as schools — might accumulate much more airborne virus, he said.

But other experts said it was difficult to extrapolate from the findings to estimate an individual’s infection risk.

https://www.nytimes.com/2020/08/11/health/coronavirus-aerosols-indoors.html

Small Mask Gaps Result in Big Efficiency Losses

A study by the University of Chicago and Argonne National Labs showed that cloth masks lose much of their efficiency due to leaks. Gaps (as caused by an improper fit of the mask) can result in over a 60% decrease in the filtration efficiency, a 1% gap reduced the filtering efficiency by half or more, emphasizing the importance of a properly fitted mask.”

https://pubs.acs.org/doi/abs/10.1021/acsnano.0c03252

VPM Research Studies Vapor Deposition on Nanofibers

Deposition of metallic vapors with anti-microbial properties on nanofibers in masks or filters offers some interesting opportunities.

The COVID-19 pandemic triggered many technical initiatives to control the spread of this highly infectious virus. However, so far only limited effort is focusing on how to detect and separate these nanoparticles (~30-150 nm in size) from breathing air, while our ability to do so would greatly impact the spread of these nanoparticles and their entry into human lungs. Thus the disciplines of filtration, filter materials, air flow management and nanoparticle containment have much to contribute to address the current crisis.

Electrospinning is an advanced electrostatic production method for nanofibers, which offer low pressure drop and high filtration efficiency in specialty filters. Many polymer materials can be processed by electrospinning, forming tangled nanofiber layers with individual fibre diameter in 10’s of nanometers. Such structure is capable to filter out 99.99+% of typical virus-size particles.
The CVD process is capable of metallizing such nanofiber structures, providing unique properties of such metallic filter for medical and demanding air filtration applications, such as sterilization and regeneration by heat or the possibility of passing electric current through such filter media.  While the example image below shows a metallized 7-micron carbon fibre, the same process can metallize nanometer-size polymer fibres with similar uniformity. 

  

August 20, 2020 - Mask Selection Webinar  Now Posted on YouTube

This webinar includes a discussion  of major issues in mask selection. It includes a presentation by Wendover Brown of Vogmask followed by a discussion with contributions from Abhisek Saha of UCSD, Christine Sun of  WFI, Kari Lukkonnen of Fibertex, and Vladimir Paserin of VPM Research. The challenge is to balance wearer protection and wearer transmission. Due to the mounting evidence that much of the transmission is airborne the needs for wearer protection are becoming paramount. This risk is further exacerbated by evidence that cloth masks act as aerosol generators for cough droplets after initial capture. More analysis needs to be done on this important phenomenon. UCSD has been doing considerable research on droplet evaporation and will be investigating the virus fate from cough droplets on surfaces and in media subjected to continuous air flow.

Vogmask is balancing the needs for air pollution and COVID  protection. This includes comfort considerations with varying degrees of exertion.  A unique design under development is a lock for a valved mask. This will provide flexibility to better balance the need.

Nanofibers offer an attractive alternative to meltblowns. Kari  Lukkonnen answered some questions about performance and availability. A number of new media options were discussed. Bob McIlvaine predicted a robust market for masks through 2025 based on increasing awareness of indoor and outdoor pollution threats,  the present viruses, the delay in achieving a fully effective vaccine against COVID and the likelihood of new viruses or at least the threat of them.

To view this YouTube recording click here: https://youtu.be/YHN49FOzJ5Q

Mask Webinar Today Probed Major Issues in Mask Selection

A 90 minute recorded webinar today reviewed major issues in mask selection. It included a presentation by Wendover Brown of Vogask followed by a discussion with contributions from Abhisek Saha of UCSD, Christine Sun of  WFI, Kari Lukkonnen of Fibertex, and Vladimir Paserin of VPM Research

Bob McIlvaine tried to frame the most important issue which is the importance of wearer protection vs wearer transmission. The McIlvaine interviews with Mann + Hummel and AAF covered ambient filtration at traffic intersections and other highly polluted outdoor locations.  Based on this vision should we tell residents of Beijing to throw away their masks? Should we tell Californians that filter cubes at strategic locations will capture the wildfire smoke and not to rely on masks to protect them? Should our strategy be to rely on preventing  COVID spread with masks having the following capabilities?

 

The group briefly discussed three points of view

A.   Masks to prevent emission are more important than masks to protect individuals

B.   Both are equally important

C.  The emphasis should be on masks to protect the wearer but with the secondary goal of preventing emission

Relative to option C Wendover Brown pointed out that  a hiker will want the air pollution protection and is far enough from others to utilize a valved mask without fear of transmission. A valved mask with a lock has the flexibility to balance comfort, protection and transmission.  Furthermore there can be instances where transmission risk can be determined by the currency of testing.

The open valve would normally be used where there is maximum distancing. However if the saliva tests prove accurate and inexpensive and the wearer has been tested within 24 hours the risk he posed with an open valve is minimal. Also since he is wearing an efficient mask his chances of becoming infected are minimal

Another aspect of the open valve is the reduction in velocity of any large cough droplet. The mask with an open valve is going to slow down and change the cough droplet trajectory.

Here is an analysis assuming that both  emitter and recipient are masked the same.

 

This analysis shows that  highly efficient masks will make a big difference. Bob McIlvaine projected substantial market growth based on communicating the health benefits from a mask program. 

Vogmask has Both Valved and Non-Valved Masks

Wendover Brown discussed the initiatives her company is pursuing as it adjusts to a market where the high efficiency mask needs of non-medical personnel are greater for COVID protection than they are for air pollutant protection.

 

In either case mask fit is very important. The filtering efficiency of a particulate respirator depends on a proper fit. This is why Vogmask supplies five sizes  S - XL. Vogmask is Quantitatively Fit Tested on human subjects to ensure the filtering efficiency is retained over a series of motions like walking, head movements, bending over, talking, etc. Here is a sample of the fit testing on Test Subjects.

 

Vogmask objectives are changing due to COVID They include

·         Meeting the demand of 9 years of customers with high public trust in brand for poor air quality, wildfire, sensitive lungs and environmentally induced illness

·         Satisfying the current requirement for highly protective, reusable, filtering masks in current crisis

·         Making a small difference in public health and health of the planet

·         Protecting the mask wearer and protecting others in public

·         Presenting comfortable mask wearing (breathing resistance, fit, quality of materials) for higher compliance in mask wearing

·         Performance and health and safety testing

The challenges to be faced include

·         Confusion among new mask wearers

·         Proper way to communicate product safety, efficiency, and environmental benefit

·         Manufacturing capacity to meet increased demand

·         Maintenance and disinfection proposals and testing

Increased manufacturing  and fulfillment capacity

·         Expanded capacity x 2 in traditional sewing plant

·         Refinements in first manufactured samples in 2^nd plant : Delays presenting to market

·         Confirm consistency across two manufacturing sites in materials, fit, feel, elasticity of thread, ear loop and trim

·         Development of Customer Service and expanded fulfillment capacity

·         Create a technologically, environmentally, and aesthetically superior product

Product Innovation & Design

·         Valve innovation with open and LOCKED position in testing

·         Improved nose band with flat coating, increased length and durability

·         Sustainable microfiber sourcing (ocean plastic sourced nylon)

Education and Marketing

·         Decision to offer No Valve products ONLY to meet current increased demand in consumer requirement for  masks

·         Commitment to educating public as information on benefit of masking evolves

 

Abhishek Saha of UCSD Focuses on Potential for Aerosol Generation from Droplets on Masks

In the webinar today Abhishek Saha of  UCSD addressed the potential for aerosols to be generated from droplets caught on masks.  He started by referencing his earlier interview with McIlvaine and the fate of droplets as salts are formed during the evaporation  process.

He then continued to describe new research into the fate of viruses in droplets landing on surfaces and those landing in the media. He pointed out that there is the potential for some of the droplet to be pushed through the media due to the fifteen breaths per minute. As the droplet evaporates the remaining salts may take a number of paths and these need further investigation.   This will be an important subject to pursue.  If it turns out that aerosols are formed from cough droplets then the whole masking program needs to be reassessed.

 

Comparison of Meltblowns and Nanofiber Mask Cleaning Impacts

 Researchers from Shinshu and Pohang Universities compared the melt-blown (MB) filter, which is commonly used for the N95 face mask, with nanofiber (NF) filter, which is also used as an effective mask filter, to evaluate their reusability. Extensive characterizations were performed repeatedly to evaluate some performance parameters, which include filtration efficiency, airflow rate, and surface and morphological properties, after two types of cleaning treatments.

In the first cleaning type, samples were dipped in 75% ethanol for a predetermined duration. In the second cleaning type, 75% ethanol was sprayed on samples. It was found that filtration efficiency of MB filter was significantly dropped after treatment with ethanol, while the NF filter exhibited consistent high filtration efficiency regardless of cleaning types. In addition, the NF filter showed better cytocompatibility than the MB filter, demonstrating its harmlessness on the human body. Regardless of ethanol treatments, surfaces of both filter types maintained hydrophobicity, which can sufficiently prevent wetting by moisture and saliva splash to prohibit not only pathogen transmission but also bacterial growth inside. On the basis of these comparative evaluations, the wider use of the NF filter for face mask applications is highly recommended, and it can be reused multiple times with robust filtration efficiency.

The MB filter exhibited better air permeability (as twice as that of NF filter) before and after treatment by ethanol, and it can be associated with higher porosity of MB filter which was recorded as high as ∼96%. NF filter had lower porosity (≲80%), and this can also be directly associated with a pressure drop which was higher (up to 183 Pa) before and after treatment with ethanol.

Because of good air permeability, pressure drop, and morphological properties regardless of ethanol treatment, both filter types qualify for the basic criteria of face mask application. However, considering the filtration efficiency aspect, while the MB filter will be effective for single use only due to its prompt reduction to ∼64% by ethanol cleaning, the NF filter might be valid for multiple reuses due to its very consistent (∼97–99%) efficiency. In addition, the NF filter did not show cytotoxicity to the tested human cells. Thus, by considering all the comparative evaluations, it can be concluded that while both MB and NF filters have similar filtration performance for single-use applications, the MB filter cannot be reused as its filtration efficiency drops drastically and the NF filter can be successfully reused multiple times after simple cleaning with ethanol.

https://pubs.acs.org/doi/10.1021/acsanm.0c01562