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

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.

After doing more research into this question, I think the answer is yes, this is actually a very good idea, only it's much more convenient to use a rubber mask brace instead of tape. I summarize my findings as well as present DIY instructions on how to do this at home in a new post: https://www.lesswrong.com/posts/CrikcGiaWK9CSSzrJ/i-made-an-n95-level-mask-at-home-and-you-can-too [LW · GW]

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.)

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.

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It is not recommended to tape surgical masks to the face to seal them airtight for several reasons. First, surgical masks are designed to be breathable, and taping them to the face can impede airflow, making it difficult to breathe. This can lead to discomfort, respiratory distress, and even hypoxia in some cases.

I don't know anyone else's answer, but for myself, while I don't want to get a serious case of COVID, I also don't necessarily want to reduce my exposure to ambient virus particles, including COVID, all the way to zero. I want just enough exposure to keep my immune system strong and active without actually getting sick and spreading diseases to others. 

Also, when I put on even a not-sealed mask with an N95 filter, I get a headache within about 10 minutes that lasts until I take it off.  This is true even at the times when I didn't realize my mask had a removable filter inserted. I would prefer not to modify my regular mask in a way that makes it more like an N95 mask unless I really need to.

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

https://smartairfilters.com/en/blog/n95-mask-surgical-prevent-transmission-coronavirus/