[Skybird]

Self-made masks are not really acceptable, they do not really protect the wearing person and not the others. After all that propaganda lies against using masks, owing to the fact that there are not enough, lets be realistic and get the production finally - finally!! - started all over the world. There is no alternative to FFP masks, period. Every other claim simply holds no substance.

And yes, people should wear these masks in town, in crowded places, and in all and every public room and shop and compartment.

In the corona crisis, long forgotten devices in the attic become attractive again. For example sewing machines: Because professional protective products are missing in many places, more and more people are making mouth-nose protectors (MNS) from fabric at home. (You can find instructions here.)

Basically, a mask can have two functions: First, it can protect other people. Ideally, anyone who is infected would spread fewer viruses around them. "Anything that minimizes the risk of infection is currently welcome," says Gerd Antes, an expert in medical statistics at the University of Freiburg. The World Health Organization (WHO) announced this week for the first time that masks could actually help to spread the Sars-CoV-2 virus.

However: "Under no circumstances should wearing an MNS or a mouth and nose covering lead to the fact that distance rules are no longer observed or recommendations for coughing and sneezing and hand hygiene are no longer implemented," warns the Robert Koch Institute. Anyone who thinks they are infected should not go out with people anyway. Not even with a mask.

A team led by Sung-Han Kim from the Asan Medical Center in Seoul reports in a recent study in the specialist magazine "Annals of Internal Medicine" that neither their professional mouth-nose protection nor a tailored model made of cotton fabric were able to Withhold Sars-CoV-2 pathogens. The researchers had four patients with Covid-19 cough on a petri dish 20 centimeters in front of their face. Then they determined the number of pathogens that had arrived there. In all three cases examined - without mouth protection, with a professional surgical mask and with a model made of fabric - large amounts of viruses were detected.

By contrast, at the end of last week a team led by Benjamin Cowling from the University of Hong Kong in the journal "Nature Medicine" reported on a study that was supposed to prove the effect of mouth-nose protection on virus retention. It was performed using a different methodology with the help of 250 patients who complained of symptoms such as fever, cough or sore throat.
Breathed in the funnel for half an hour

The subjects were infected with various types of viruses, and a total of 17 percent were found to have coronaviruses - but not of the Sars-CoV-2 type, because the study was running before the pathogen became known. However, according to Cowling, the size of the viruses is very similar, so the novel corona virus should behave in a comparable manner.

Half of the patients were given commercially produced surgical masks and put them on themselves, while the other half had their faces completely uncovered. Then everyone had to breathe into a machine with a kind of funnel for half an hour and cough if necessary. It was found that the coronaviruses were retained in all cases in the patients with masks. They were not detectable in the exhaled air either in droplets or in the form of fine aerosols.

However, and this is an important limitation, the trials in Hong Kong were not carried out with self-made face shields, but with professionally made ones. A study from Great Britain, which is already some years old, indicates that self-made masks could deliver worse results.

At that time, researchers compared the efficiency of masks made from T-shirt fabric to retain influenza viruses with a commercially available product. On the one hand, it was shown that self-made masks are generally better than nothing. At the same time, however, they only achieved around a third of the restraining power of the surgical masks. This obviously has to do with the fact that the self-made masks simply don't fit so well.
"... but you also have to breathe"

In theory, a second function of mouth-nose masks could also be self-protection against the Sars-CoV-2 virus. This usually requires special masks of the FFP-2 or FFP-3 standards, which are particularly scarce. "FFP2 / 3 masks should continue to be reserved for the medical, nursing and special professional groups," wrote the National Academy of Sciences, Leopoldina, in its latest statement.

Could cloth masks also protect against the virus to a certain extent? "Mouth and nose protection also serves directly to protect yourself to a limited extent," writes the Leopoldina. Manufacturers of professional protective equipment, on the other hand, say that simple textiles do not protect against pathogens - because they do not have a filter: Textile masks "might help against the cold or the sun, but not against viruses".

But what if you upgraded the fabric masks you made yourself with a filter? Some researchers are now investigating possible material for this. This must not allow viruses to pass through, but air must still be able to pass through as well as possible. "You need something that removes particles efficiently, but you also need to breathe," environmental engineer Yang Wang of the Missouri University of Science and Technology summarized the problem in the New York Times.

For example, Wang experimented with filters used in air conditioners. Arranged in several layers, these could in principle retain up to 95 percent of the particles. However, they pose health risks - because they can release fibers that can then be inhaled and damage the lungs. This is not an option for self-made.
A vacuum cleaner bag? The manufacturer warns of this

Similar problems could also arise with the use of vacuum cleaner bags for filter construction. These could also contain glass fibers. Interior designer Jiangmei Wu from Indiana University developed the instructions for an origami mask that is made from vacuum cleaner bags. However, it is important that it uses material without glass fibers.

According to the New York Times, tests at Missouri University and the University of Virginia have shown that vacuum cleaner bags can reduce particle pollution by 60 to 87 percent. However, manufacturers such as the Melitta Group explicitly warn against the use of vacuum cleaner bags. Corona viruses are smaller than the fine dust for which the filter was developed. In addition, the fit of self-made masks is bad.
Simple test when looking into the light

Wang's team also experimented with multiple layers of fabric, one on top of the other. Specifically, he used pillowcases made of high-quality fabric with a thread count of 600, so the fabric has 600 horizontal and vertical threads per square centimeter. A double layer of such material held back 22 percent of the particles, four layers of fabric on top of each other reached a value of almost 60 percent. In the test, a double-layered scarf made of thick wool yarn had a filter performance of 21 percent, a double-layered bandana made of cotton a good 18 percent. It is not much.

Anesthetist Scott Segal from the Wake Forest Baptist Medical Center in Winston-Salem (North Carolina) also found out how useful at least several layers of fabric can be. He has a comparatively simple tip: You have to hold the self-made fabric mask against the light. If it seems "really light" through the fibers, it is "not a good fabric". If, on the other hand, it is "a denser mesh", "then this is the material that you want to use".

A possible insert for self-made fabric masks could theoretically also be coffee filters. Here, Yang's team came up with a filter performance of 40 to 50 percent in the experiments. However, three layers of filter paper had to be placed on top of each other. In this case, breathing is difficult, the scientists say. This option is also suboptimal.

So what's left? The results of Wang and Segal have so far not been published in a peer-reviewed scientific journal. There is no recipe for the perfect self-made mask. The discussion about this will certainly continue, at the latest when the currently strict starting and contact rules end. Because: "A gradual relaxation of the restrictions", writes the Leopoldina, "should go hand in hand with the full coverage of mouth and nose protection". Bavaria's Prime Minister Söder claims that mask masking is coming.

Sad that something obvious since weeks and months must be defended against the most irrational and stupid lies one could imagine. Macronman for example until today claims that masks even do the opposite and are a health hazard to people wearing them.

Quite some people become angry if you tell them obvious blatant lies time and again, crowds are stupid - but this stupid they are not. Angry they become because it is offensive if you tell somebody to his face that you take him as an intellectually incapacitated total idiot.


What? There are too few FFP masks? They talk about billions and trillions and move heaven and earth and have other branches of indutstry chiming in into producing ventilators and life support devices - but since weeks cannot get the emergency quick-building of new factories for FFP masks in all Western countries started although quite some companies stand ready to produce both filter material and fibres if their requests for credit securities wpould be met with a bit more wellmeaning...??? Fire this useless political personnel then! I thought we are in a desperate emergency...? And all they get managed is that a few T-Shirt preducers now knit oridnary textile masks of questionable medical value? Sorry, dear drama conductors, that is unacceptable as a performance.