Why don't we tape surgical masks to the face to seal them airtight?

post by ChristianKl · 2020-04-14T08:33:14.637Z · score: 16 (6 votes) · LW · GW · 1 comment

This is a question post.


    13 gjm
    5 Spiracular
    3 Stuart Anderson
    2 jimrandomh
    1 edi
1 comment

As far as I understand the prime advantage of surgical masks over N95 masks lies in the N95 masks being able to seal and filter all of the air while the surgical masks allow air to pass at their sides.

Given that there are many situations where people would ideally wear N95 masks but have only access to surgical masks, why can't we improve the surgical masks by using adhesive tape to seal their borders to the face?


answer by gjm · 2020-04-14T09:32:24.655Z · score: 13 (5 votes) · LW(p) · GW(p)

I'm not sure you're right about the advantages of N95 masks over surgical masks. (Note: at present the question says "... the prime advantage of surgical masks over N95 masks ..." but I assume that's just a slip.)

N95 masks have finer filters that keep out particles smaller than surgical masks' filters do. If you tape a surgical mask to your face in a way that seals it perfectly, then while you may be doing a better job of keeping out the particles the mask can block you're still not doing much for the smaller ones.

N95 masks are notoriously tricky to fit well, but so far as I know no one tapes those to their faces. Whatever the reasons for that, many of those reasons probably apply to surgical masks (but more so, because the benefit will be smaller, because however good the fit the surgical masks are still not keeping out all the smaller particles.) I don't know those reasons, but I guess they include the following, all of which seem like they apply to surgical masks:

  • Taping a mask to your face is harder than it may sound. There isn't that much available surface between nose and eyes to tape to.
  • Your face is flexible and moves around as you talk, blink, smile, etc. Tape can peel off. Especially if you have facial hair, wrinkles, damage from earlier mask-unpeelings, etc., rather than a perfect smooth surface to tape to.
  • Surgical masks are also flexible and often have folds extending to their edges, making it difficult to seal them effectively using tape.
  • They also have straps. It seems to me that any way of taping a mask on is going to leave a "tunnel" along the straps. You can tape the straps down but they're inevitably going to move around in ways that tend to enlarge that tunnel.
  • Peeling tape off your face is painful and may do damage, especially if you are doing it repeatedly and especially if the tape is extra-sticky so as not to peel off while you're wearing the mask.
  • The slow and awkward peeling-off process keeps the mask, whose outer surface might be covered in virus particles or whatever, close to your face for longer while you're removing it.

None of this means that taping down a surgical mask won't provide any benefit. My guess is that it does. But I suspect the benefit is small enough, and the pain and inconvenience large enough, that most people won't consider it a good tradeoff.

As to whether that's right in any given case, I don't know. It would be interesting to have some actual numbers on this, but my guess is that no one's done the studies.

comment by kithpendragon · 2020-04-14T12:39:41.438Z · score: 2 (2 votes) · LW(p) · GW(p)

I think you could overcome most of those bullet points by using spirit gum instead of tape, tho I'm not sure how often you'd want to do that: even sticking an adhesive bandage to some patch of skin and changing it every day will do considerable damage after a relatively short time.

I've also come to understand that the N95 respirator is a much better filter than the paper masks could ever be, so adhering paper masks to the face might simply be nowhere near as useful as just having the right mask in the first place. My understanding is that most masks are simply just at keeping the user's bio-bits out of the environment than they are at keeping the environment out of the user. That's why the current recommendation is for the general public to use paper or cloth masks while reserving N95 respirators for healthcare personnel.

comment by gilch · 2020-04-15T05:55:55.230Z · score: 2 (2 votes) · LW(p) · GW(p)

Sticking it to your face every day for your job might be a problem, but what if you're only using it once a week to buy groceries? Maybe the better fit with no training is worth the skin damage in this case.

comment by gjm · 2020-04-14T14:15:26.489Z · score: 2 (1 votes) · LW(p) · GW(p)

Right. Though the paper by Davies et al that Christian found suggests that at least some paper masks may not be so wretched at keeping out tiny particles.

comment by ChristianKl · 2020-04-14T13:55:50.628Z · score: 2 (1 votes) · LW(p) · GW(p)

N95 masks just need to filter 95% to get that certification. They don't filter as much as FFP3 masks but only as much as FFP2 masks. They aren't equipment that keeps out all the smaller particles.

Davis et al 2013 suggests ~90% filtration for surgical masks. I read somewhere in the literature that in cases where studies found similar effects for protection by surgical masks and N95 masks it's likely because the N95 masks didn't fit correctly.

comment by gjm · 2020-04-14T14:14:34.906Z · score: 2 (1 votes) · LW(p) · GW(p)

Davies et al is encouraging as regards the benefits of surgical masks. Still, letting 10% in is a lot worse than letting 5% in, and the fact that the Wikipedia page about N95 masks says "Collection efficiency of surgical mask filters can range from less than 10% to nearly 90% for different manufacturers’ masks when measured using the test parameters for NIOSH certification" suggests that maybe Davies et al got lucky in which surgical masks they tested.

answer by Spiracular · 2020-05-12T21:48:30.494Z · score: 5 (3 votes) · LW(p) · GW(p)

I've personally found that just stapling shut the outer edge of the first fold on either side of a surgical mask results in a mask that mostly sucks to my face when I breathe in. It doesn't stick well when I breathe out, though.

This is much easier to implement than fancy adherents; all it takes is 2 staples and a stapler, or a needle and thread. It struck me as a plausible 80-20. (Well, less than 80%. Obviously, this is no N95.)

(It might only work for some face-shapes, though.)

This generates a new problem, which would also apply to taped/glued solutions:

The front is made of a softer fabric than N95s. After an hour of wear, it will suck to my lips if I breathe in with my mouth. And since it doesn't stick on out-breaths, air still gets out the sides and sometimes the top. I don't know how much additional risk this presents, but I would be curious to hear someone weigh in.

(It also has uncomfortably-high humidity, but that's even more true of N95s.)

answer by Stuart Anderson · 2020-04-14T13:49:39.819Z · score: 3 (2 votes) · LW(p) · GW(p)

Surgical masks aren't of the same grade of filtering material that N95 is, so taping them up is probably pointless.

My understanding is surgical masks are primarily about protecting the patient/others from one's own germs, not the other way around. All the covid wards I've seen are using N95 masks plus face shields and other PPE. There are plenty of photos of clinicians with marks and wounds on their faces from their PPE, so I assume that they can do a near airtight fit when used correctly.

The question I have is can we make a hood that has an N95 filter and is run at positive pressure with a pump? That's going to be the reverse of a surgical mask (ie. it will spray your germs everywhere but prevent other people's germs getting to you).

comment by Anonymous2_4_7 (jakepenkethman-hotmail-co-uk) · 2020-04-28T22:38:39.546Z · score: 2 (1 votes) · LW(p) · GW(p)

I treated a COVID patient today and did just this. It was really easy to use a skin friendly hypafix or mepore that you can cut and fit around your eyes to seal tight the mask. I certainly felt more protected.

comment by jmh · 2020-04-15T00:01:03.199Z · score: 1 (1 votes) · LW(p) · GW(p)

I saw a picture in one of the Philippine papers I read periodically during the week. The man had taken a water dispenser jug and cut the bottom off, and shaped it to fit over his shoulders.

I'm not sure what he did about the top (I'm guessing plugged or taped it but not clear in the picture. I was thinking you could do something with that like, a good find filter paper at the bottom, a back back with some type of canister type filtered intake air and a small fan/blower (say from a computer) to assist air intake and vacuum cleaner hose to the top.

With the right filters you probably cover both intake and exhaust air.

Just might have a problem grabbing a cab or uber ride -- or your own car unless convertible or sunroof.

answer by jimrandomh · 2020-05-08T05:33:33.369Z · score: 2 (1 votes) · LW(p) · GW(p)

As a diabetic, I have a few things (insulin infusion canula, continuous glucose monitor) that attach to skin with adhesive. In principle, you could use medical tape around the edges of a normal mask, and it would improve the seal. I think the reason people don't do this is because it's a lot of effort to put on (effort which could be spent improving the fit in other ways), and it's physically painful to take off. This limits its usefulness to the range where an imperfectly-fitted N95 isn't good enough, but a positive-pressure suite isn't necessary; I'm not sure situations in that range are at all common.

answer by edi · 2020-05-07T20:16:53.318Z · score: 1 (1 votes) · LW(p) · GW(p)

This article here suggests that N95 and surgical masks performances were similar while preventing to catch the flu.


comment by ChristianKl · 2020-05-08T11:37:39.778Z · score: 2 (1 votes) · LW(p) · GW(p)

There are multiple studies that tested both. One explanation for the result of that study is that the N95 weren't properly fitted and didn't provided the added advantages that fitted masks provide.

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comment by jmh · 2020-04-14T13:43:33.126Z · score: 6 (5 votes) · LW(p) · GW(p)

I agree that tape should improve the value of the surgical mask. I've seen a number of quality respirators that will use a rubber or silicon face mask that will seal much better than the standard N95 mask people are buying. That allows the ability to actually "seat" the mask to your face and improve the seal.

However, as others point out, that doesn't change the size of the particles that are filtered. So I wonder just how much that might really help.

The surgical mask is not designed, or really intended, to protect the wearer from the external environment but the external environment (to a certain extent) from the wearer. It seems to be something of a deflection and catch device. Taping the mask might then increase the velocity of any particles passing through the surgical mask, thus spreading them more widely, as none is now deflected to the side and a bit backwards.