Big and Small

In the UK people have been talking about lifting lockdown, with the mandatory wearing of masks in public places. My gut feel is that our government is libertarian in nature, so won’t go near that. They might advise, but I doubt they’ll mandate. “Experts” seem split on whether they are effective or not (the masks, not the government. Everybody is pretty unanimous about the government!) I think it is a case of choose an expert who fits in with what you already think. So one of the questions I have had on my list of things I really need to do, (and sooner rather than later) has been to evaluate the question of just how much use a facemask would be.

I started off, I must admit, thinking: particles small, gaps in the mesh of facemask fibres big, so really did not see the point in wearing one. But I might be changing my mind.

My plan this morning was to find out the size of your average COVID-19 particle, then to research the denier scale, previously encoutered only in the context of women’s tights! My gut feel was that gaps between fibres would be enormous in comparison to the size of this virus.

I ran out of time (I needed to call people) so I never got to find out about Denier. For all I know, it could be the wrong thing entirely. I did have some success, though. My very first hit yielded me a virus size of 0.02 microns. A micron is just 10-6m. That’s actually quite large – okay, well, it’s small, but it is more than a million times bigger than an atom, say, which comes in at roughly 10-15m. Something like my water filter claims to trap particles of that kind of size. If only I could breathe through my water filter, I’d drown instead 😆

Actually the graph that came with that number was interesting. They might have already done the work for me. I don’t own the copyright on any of this, so will just link to their graph and cross my fingers that it stays good.


So the material used to make a surgical mask will filter out 89% of particles which are the same size as COVID. Now, I have no idea who the authors are, how reputable they are, but I thought the image represented a useful start point for later. They at least read as pretty serious.

The thing I picked up from this is that even just a (presumably knitted, common-or-garden) scarf might halve the flow of covid-sized particles. So maybe I will be changing my mind after all about masks.

Probably, more to come on this one.


  1. I don’t wear a mask while out walking in the street but do wear one while inside a shop – here in Scotland we’ve been asked to cover our faces while in enclosed public spaces (like shops or on public transport), so I do as I’m asked. No idea if it helps or hinders, but we’ve been asked to wear a mask by our Government so… even if all it does is make people feel better about being out and about – well I’m all for the placebo effect!

    Liked by 2 people

    • I’d like to be convinced of the value before I wear one. I certainly don’t trust that the government will offer the best (medical) advice, so I want to know for myself. It’s made worse that most of these masks, somebody has just run up on their sewing machine, that hardly makes me feel that anybody is being protected.

      Liked by 2 people

  2. I look forward to hearing more of your research.

    As I understand it*, the main purpose of masks is to prevent the one wearing the mask from spreading the virus through spraying spittle — not the other way around.

    could be completely wrong

    Liked by 1 person

    • what is the general feeling in Ca about them? Do your government recommend wearing them? Are any members of your government wearing them? My wife waved a simple cloth mask in front of me, but I have never worn it. Neither of us wears a mask.


      • Canadian government recommend you wear a mask in public, but not mandatory. With stores, its hit and miss, some stores it’s mandatory to wear a mask and they are willing to sell you one at the entrance for $6, other it’s not mandatory, but there are one-way aisles and you have to follow the arrows. If politicians are on photo ops they wear a mask, otherwise not.

        Liked by 1 person

  3. Reblogged this on Mister Bump and commented:

    Just as a follow-on from my earlier post, where I got as far as having discovered that virus particles are about 0.02 microns in size.

    A bit more time today, and a bit more digging.

    I didn’t bother with Denier, overnight I decided that was probably a red herring.

    I did, however, find a UK company called Filtrex. I had in my mind something like DIY masks for sanding etc. but these guys seem far more upmarket – clean rooms etc. On their site, I found a useful page which talked about stan0dards. Apparently there is one, ISO 16890. It only came about in 2016 so I suspect it isn’t ubiquitous yet. Bottom line, it splits filters into four levels, and even the highest quality of these only filters particles of 0.3-1 micron. That’s still an order of magnitude bigger than COVID-19. Imagine trying to get a yardstick through a 10-yard gap…. Conclusion – I’m looking in the wrong ballpark.

    I then started looking at other standards. I came across FFP1, 2 and 3, which I think are EU standards. FFP = filtering facepiece. The masks gradually restrict smaller particles. with FFP3 offering the highest level of protection.

    FFP3 masks are what is used by our NHS to care for COVID patients, with a big caveat that if you’re working in the NHS, these masks are supposed to be fitted to your face, so there’s no gap. With all the hoo-ha here about PPE, I have no idea whether that is actually happening, but it is what is supposed to happen.

    FFP3 is also the type of mask recommended by the WHO to treat COVID patients – reassuring that in this case at least, we are fitting in with international standards. On some sites I have seen that it is the equivalent of N99. Funny, Jim Adams mentioned an N-rating after my original post, yesterday, but I couldn’t dig up any info. I’m guessing it is the corresponding US standard.

    FFP3 masks seem to be retailing on eBay at around GBP20 minimum. That’s not far different in USD or EUR, and that’s each. Pretty blatant profiteering, most likely.

    Nevertheless I might get one with a view to washing it between trips out, although that is bloody expensive just for a mask. And before I buy anything I’ll need to be clear whether it is washable or not.

    Even after that, I’m not sure that they will be a barrier, but I’m guessing that since the NHS use this standard of mask, it’ll be the best I can get hold of. I might have to settle for that. Given this appears to be a european standard, and we have been in the EU for forty-odd years, I wouldn’t expect to have to look for any other standards.


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