McIlvaine Coronavirus Market Ale

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Over the next six months many thousands of lives will be saved if people start wearing efficient face masks. Efficient tight fitting masks provide much better protection than loose inefficient masks. The virus travels in small aerosols. Even the small amount in large cough droplets is only temporarily captured before evaporation and turbulence cause it to again become airborne.

The mask should be viewed as a sophisticated medical device. It has to utilize filtration media which can capture particles as small as 0.1 microns. It has to minimize leakage of air around the periphery despite the fact that a face is not a smooth surface. Furthermore there is a big difference among face shapes and sizes.

Because the mask may be worn for long periods it needs to be comfortable. It is also an article of clothing so attractiveness matters.

Mask life is another factor. The mask can be disposable or reusable. If it is reusable it must remain viable through some number of cleaning cycles.

The public needs masks which are Comfortable, Attractive, Tight fitting, Efficient, Reusable. This forms the acronym CATER. Due to all the complexities it is highly desirable that all the information on CATER masks be made available and analysed. The McIlvaine Company has been doing this for all mask types in Coronavirus Technology Solutions. However this is a paid service beyond the price range of the individual. McIlvaine is therefore offering a free option.

CATER Mask Decisions has guidance, background documents and multiple Alerts per week. The goal is to provide individuals and organizations with the information they need to make the best mask decisions.

CATER Mask Decisions provides the evidence which is needed by associations and government bodies to provide guidance to mask wearers. The Waterloo Filtration Institute is one of the associations which can evaluate this evidence and provide guidance. McIlvaine has proposed to WFI that it set up procedures whereby suppliers can submit evidence about their masks and receive evaluations.

Since WFI members include many experts in media, monitoring and other key areas, they will be able to provide evaluation systems which will be of maximum value to decision makers.

McIlvaine recommends consideration of evaluations which include media efficiency less unfiltered leakage. The media efficiency will be straight forward but there are many variables in the unfiltered leakage including numbers of mask sizes, face dimensions, and movement,. The evaluation can reflect the amount of evidence presented by the supplier. McIlvaine is endeavoring to provide the background evidence such as is supplied in the balance of this Alert.

It was originally thought that no COVID was airborne. Then it was realized that some is airborne but that this was small compared to the virus in cough and sneeze droplets. Research then showed that most virus is released in small droplets as we talk and even breath. The latest research shows that droplets temporarily captured on mask surfaces can become smaller droplets or evaporate and become a transmission source.

This evolution in thinking has led to the widespread mask mandates. However because the virus will penetrate inefficient filters and navigate around masks which are not tight fitting some masks can be 10 times more effective than others. A mask mandate which does not include mask effectiveness is not meaningful. It is therefore a matter of highest importance to determine effectiveness of different mask types and educate purchasers to make the right choices.

Mask filter media efficiency is a function of the particle sizes to be removed. The first problem is that viruses can be carried by small particulates of various different shapes and specific gravities. Equipment to measure the efficiency of removal versus particle size attempt to normalize particle diameter for non-spheres and assume that all the particles have the same specific gravity.

The industry uses a device called a cascade impactor to measure the weight fraction by particle size. Particles which impinge at increasing velocities define the size segmentation. Particle counters use various means to count the number of particles in various size ranges. In all cases they are reduced to spherical equivalents.

Two filters may provide equally high removal efficiency on 0.3 particles. In the case below one has much higher efficiency on 0.1 micron particles but lower efficiency on 0.5 micron particles.

Since the virus may be attached to 0.05 micron particles, to 0.3 micron particles or in 1 micron droplets there will be differences in virus removal which are difficult to determine.

All of this equipment is designed to determine the temporary capture of particles. It does not take into account the capture of droplets which then evaporate or split allowing droplets or salts to penetrate the media.

It would be nice if there were a testing device similar to what McIlvaine developed for particulate capture in scrubbers. The McIlvaine Mini Scrubber is a 1 cfm device which measures particle emissions with various scrubber energy inputs. However, no direct reading device such as this is available for virus capture measurement.

· Any efficiency requirements in regulations should not be adopted for other than the intended purpose without analysis

Because the virus travels through the air as would perfume or cigarette smoke it will flow around mask filter media and through any openings. Therefore the mask fit is very important. The amount of virus in the unfiltered air will be directly proportional to the percentage of total air. Here two examples of masks.

Mask	Efficiency %	Unfiltered %	Net Efficiency
Tight /Efficient	93	-4	89
Loose/Inefficient	60	-40	36

Because the loose inefficient mask allows 40% of the air to escape unfiltered the media only removes 60% of the remaining 60% resulting in a net efficiency of only 36%

Some masks have net efficiencies as low as 10%. This means that there is at least a nine fold difference in effectiveness between masks. The more efficient cloth masks are generally ones with higher resistance which means that more air is likely to leak around the mask. It is therefore critical to determine the amount of unfiltered or leaked air.

There has been very extensive testing of filter media. Fit testing for medical N 95 masks has been refined and is reliable. Both qualitative and quantitative tests are being used.

A few companies offering masks to the public have done fit testing. It is very time consuming and expensive. There are four variables

One company has five different mask sizes and has conducted fit testing through BSI Group (British Standards)

Surgical mask material is fairly good for trapping viruses, but surgical masks as normally worn by themselves are not very effective at protecting you because they are not sealed. The main reason surgical masks fail to protect people is air leakage around the mask, whereby viruses can just easily go around the mask and into your nose and mouth. The amount of air going around a mask is known as "total inward leakage (TIL)" in scientific research.

For example, a study of manikins wearing face masks showed that typical total inward leakage often exceeded 25%.

Alert November 16 - University of Tokyo; Net Efficiency: Cloth 17%, Surgical 47%, N95 79%

Researchers in Japan say they have confirmed that face masks are effective in both retarding the spread of viruses and reducing the intake of them. They used actual coronaviruses and mannequins to reach that conclusion.

The finding was made by a group led by Professor Kawaoka Yoshihiro and Project Assistant Professor Ueki Hiroshi at the University of Tokyo's Institute of Medical Science.

In their experiments, they placed two mannequins face-to-face in a laboratory. One was designed to discharge airborne droplets containing the coronaviruses. The other had a mechanism enabling it to take in air, imitating human breathing.

In one experiment, the researchers put a mask on the inhaling mannequin. They say the amount of viruses it absorbed was cut by 17 percent with a cloth mask and by 47 percent with an ordinary surgical mask. When they put an N95 medical mask on the mannequin so it fitted snugly, the amount declined by 79 percent.

The 3M masks consistently performed the best in these tests. The Vogmask performed fairly well, capturing 95% of pollutants. Big-name masks like the Respro and Totobobo masks both captured less than 85% of pollutants.

It’s important to make clear: masks that fit my face well might not fit other people’s faces well. However, there is evidence from a broader population that masks fit most people well. A scientific study of 3M models on 22 Chinese people found a median fit score of 99.5%–essentially the same as the top results from Dr. Saint Cyr and me.

Chinese masks which showed that even if the efficiency rating was high, the leakage during normal activity could be 66%. Researchers first tested each mask’s filtration efficiency by drawing airborne diesel exhaust through a section of the material for 30 minutes and measuring the particulate matter and black carbon concentrations on both sides. They also tested four masks on 10 volunteers who were exposed to diesel exhaust in a lab while performing tasks such as talking, sitting, standing, bending over and walking in place.

In the filtration tests, the average particle and carbon penetration ranged from 0.26 percent to 29 percent, depending on the mask material. In the volunteers, the average leakage around mask edges ranged from 3 percent to 68 percent during sedentary tasks and 7 percent to 66 percent in active tasks. Only one mask had an average leakage below 10 percent in both active and sedentary tests.

Alert August 14 - With Leaks, Droplets Temporarily Captured are Later Transmitted

One of the subjects for discussion will be the measurement of one stop mask efficiency vs direct flight. An airline passenger can fly from Seattle to Atlanta where he infects the recipient. Without a mask the Atlanta recipient receives the full virus load. But most Seattle to Atlanta flights stop in Denver. So in this example with the mask being Denver the full virus load lands in this hub. But what happens to it subsequently?

As the millions of deposited viruses start to evaporate or catch the flight from the hub some will end up in Atlanta but others will end up in Chicago and Dallas. In all likelihood an inefficient mask acts as a hub and distributes all the virus passengers in a cough in many different directions.

The original guidance of CDC that masks should be used primarily to catch the large cough and sneeze droplets is based on the assumption that it takes millions of viral particles to infect someone. Furthermore it was originally presumed that viruses will not be airborne and if they are they die quickly. All of these assumptions have been proven to be inaccurate.

With the one stop or hub and spoke flight pattern you more than likely have only thousands or hundreds of virus particles reaching Kansas City or Albuquerque.

However, if every infected cougher is wearing a cloth mask there will be many transmitters generating hundreds or thousands of viral particles. The recipient may be receiving the millions of virus particles over time from many different transmitters.

Some studies in hospitals address the cumulative effect and conclude that it is significant. Others establish the long distance travel and survival of viruses. Other studies show that some viruses become dormant but are revived by the moisture in the lungs. This deep penetration can lead to more serious infection than larger virus droplets in the nasal passages.

Another way to analyze the problem would be the example of an infected healthcare worker and an elderly non infected patient. The worker is with the patient for an hour and coughs into a mask. Over the hour the patient may receive as many virus particles from the worker as he would have received in the initial cough if the health care worker had been mask less.

Alert November 25 - Vogmask Shows Inward Leakage of 2-8% with a Variety of Movements

Fit testing for the public requires a different system than for healthcare workers. For someone in a hospital setting there are both qualitative and quantitative fit testing methods. But they require tests of individuals.

For masks used by the public the best approach is to use a panel of people of different sizes, provide appropriate masks for each and then test leakage under various conditions. One company has invested heavily in this approach.

Vogmask has Quantitatively Fit Tested 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.

The determination of a leakage rating is therefore more subjective and requires a different validation approach. An expert reviewing the Vogmask data would have confidence that the leakage range is within the 1-8% range. It is therefore recommended that a validation group be formed to provide impartial judgements on data submitted by mask makers

The efficiency and face seal leakage characteristics of two half masks equipped with particle filters or gas filters, and of two surgical masks were studied by means of a test head connected to a breathing machine. Filtration and leakage were studied as a function of particle size over a diameter range of 0.3-10 micron with corn oil aerosol and an optical particle counter. The filtration efficiency of the filter materials was good, over 95%, for particles above 5 micron in diameter but great variation existed for smaller particles. The face seal leakage was manifested as decreased efficiency for large particles and also for total mass, while the particles in the micrometer range contained the major part of the test aerosol mass. The particle number efficiency diagrams obtained can be used both in filter material studies and in leak detection of valves or filter housings

Computer modelling by researchers in the US reveals that standard recommended face masks have more leaks when used by women. Photo: Shutterstock

Standard face masks recommended by US health authorities are not a good fit for women – or the elderly or thin people, according to a new study.

Researchers led by Dr Kourosh Shoele at Florida State University found that masks recommended by the US Centres for Disease Control and Prevention to stop the spread of

But “leakage” from the mask of the suggested size and design doubled when used by women because the protective equipment was too big. This was also the case with thin or elderly users.

“Different mask designs should be recommended for different categories of people, especially based on weight, age, and gender,” the team said in a non-peer-reviewed paper posted on the preprint site medRxiv.org

Shoele’s team also found that a mask’s fit over the chin was a problem for people who were underweight. For the same reason, the elderly also had a greater gap than the young during routine daily activities such as talking and breathing, according to the computer simulation.

Women in the United States are already more likely than men to wear a face mask, according to a separate study.

They also do so with greater care. Across the US, more 55 per cent of women wore masks as recommended compared with 38 per cent of men, researchers at New York University and Yale University said in a paper published in the journal Behavioural Science and Policy.