[Jolly2 (OP)]

We need a new type of medical small-replaceable-filter mask.

To save resources surely it is possible to create a mask where you simply have to replace a small fabric filter?

Apparently Corona virus is rather larger so simple dust mask should protect people.

[Bored chemist]

The filter is easy.
Getting it sealed to the face is the tricky bit.

You have nearly reinvented the cartridge respirator.
https://en.wikipedia.org/wiki/Respirator#Chemical_cartridge

Apparently Corona virus is rather larger

At 125 nM diameter it's big for a virus, but still a nanoscale object.
This is not a job for a handkerchief.

[Colin2B]

We need a new type of medical small-replaceable-filter mask.

To save resources surely it is possible to create a mask where you simply have to replace a small fabric filter?

One of the big advantages of the simple masks is they are disposable, rather than having to sterilise.

[alancalverd]

It's a good idea to produce a well-fitting personal mask with a replaceable filter. Although the virus will pass through most simple filters, it's droplet-borne so the filter should contain the droplets.

[Jolly2 (OP)]

We need a new type of medical small-replaceable-filter mask.

To save resources surely it is possible to create a mask where you simply have to replace a small fabric filter?

One of the big advantages of the simple masks is they are disposable, rather than having to sterilise.

Sure, but considering that, everyone wants masks at the same time, currently we have a shortage... sterilisation is a better option.
Apparently 30 minutes in an oven over 70 degrees Celsius should be sufficient to destroy the Corona virus. 
Oven heating is better then steaming or washing which can destroy the fabric and reduce the effectiveness of the mask.

[Jolly2 (OP)]

The filter is easy.
Getting it sealed to the face is the tricky bit.

You have nearly reinvented the cartridge respirator.
https://en.wikipedia.org/wiki/Respirator#Chemical_cartridge

Apparently Corona virus is rather larger

At 125 nM diameter it's big for a virus, but still a nanoscale object.
This is not a job for a handkerchief.

Yeah, personally while people wait for stocks of masks to come back.  Probably best people make their own masks.

Thank you for listing the actual size of the virus.

As best I can tell 'Felt' is probably the best material to make a mask from, it's used extensively to produce air filters.

But I suppose Hoover bags could also be repurposed provided they restrict anything over 125 nM.

Apparently in the Czech Republic they have gained masks for the entire population by making masks themselves at home.


Everyone wears a mask seems to be the best strategy, with an effective mask contagious people cant spread and healthy people can't catch it. Everyone needs to wear a mask, if everyone did there would be no need for a lock down...

Apparently now law in Bulgaria and Austria that all people have to wear masks outside.

[Jolly2 (OP)]

Change threat best home made mask ideas...

[Jolly2 (OP)]

At 125 nM diameter it's big for a virus, but still a nanoscale object.

Can I ask where you got the size from because actually you have referenced a size less then a micron.
Less then a micron is an understatement. I was under the impression the virus was considerably bigger.

Dont worry I found a few sourses ... https://smartairfilters.com/en/blog/coronavirus-pollution-masks-n95-surgical-mask/

125 nano microns it is.

[Colin2B]

We need a new type of medical small-replaceable-filter mask.

To save resources surely it is possible to create a mask where you simply have to replace a small fabric filter?

One of the big advantages of the simple masks is they are disposable, rather than having to sterilise.

Sure, but considering that, everyone wants masks at the same time, currently we have a shortage... sterilisation is a better option.
Apparently 30 minutes in an oven over 70 degrees Celsius should be sufficient to destroy the Corona virus. 
Oven heating is better then steaming or washing which can destroy the fabric and reduce the effectiveness of the mask.

I would agree that sterilisation would be a useful option, but having replaceable filters complicates the process as you have 2 parts to separate and sterilise. Probably better to use simple masks and sterilise those.

[Bored chemist]

There are several threads talking about masks.
None asks how good they need to be.

The current estimate for R0 is about 2 or 3. Each infected individual infects about 2 or 3  others.
If we can reduce that below 1 the pandemic dies out.

The actual data about surgical masks (measured with influenza virus, but, as Alan pointed out, it's the size of the exhaled particles that matters, rather than the virus) is here
https://www.hse.gov.uk/research/rrpdf/rr619.pdf
And here's part of the summary.
"Main Findings
This study focussed on the effectiveness of surgical masks against a range of airborne particles.
Using separate tests to measure levels of inert particles and live aerosolised influenza virus, our
findings show that surgical masks provide around a 6-fold reduction in exposure. Live viruses
could be detected in the air behind all surgical masks tested. By contrast, properly fitted
respirators could provide at least a 100-fold reduction. "

Evena a six fold reduction in virus, if it resulted in a 6 fold reduction in transmission, would be sufficient to reduce R0  to about 0.3 to 0.5.
Since that's less than 1 the pandemic would, in principle be halted by such measures.

Of course, there's an assumption in there which is questionable, but it's important to recognise that, even a small reduction is enough.

[Colin2B]

The other thing that would help front line staff would be goggles or face shields to guard against coughs/sneezing.

I notice that govt is now delivering P3 masks to frontline ie PF = up to 100

You read it here first!

[Colin2B]

New data on expulsion of droplet/aerosol cloud shows much greater range than previously thought.
https://jamanetwork.com/journals/jama/fullarticle/2763852

[Jolly2 (OP)]

New data on expulsion of droplet/aerosol cloud shows much greater range than previously thought.
https://jamanetwork.com/journals/jama/fullarticle/2763852

It depends on the size the droplets and particles. Larger droplets fall to the group quiet quickly but smaller particles can hang around In the air for at least 30 minutes according to a Chinese study I saw.

If everyone wears a mask that is seriously reduced.