Science desk
< September 2	<< Aug \| September \| Oct >>	September 4 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

September 3[edit]

valved n95 respirators[edit]

It's still very hard to get unvalved n95 respirators, but valved ones (not recommended for virus protection because the exhaust port spews virus if you are infected) are getting easier to find. Home Depot near here has some. 1) Does snipping out the valve and patching the hole with a rubber seal sound like a reasonable fix to this issue? The seal would probably be a bit of cut-up nitrile glove hot-glued into the mask. From the picture I think the hole would be maybe 15mm diameter. 2) Why after all this time are regular n95 still so hard to get? There's no toilet paper shortage any more, for example. Thanks. 2601:648:8202:96B0:0:0:0:DDAF (talk) 05:47, 3 September 2020 (UTC)[reply]

I once ordered and wore a valved N95 (FFP2 in the EU) mask during pandemic. The valve there is for a reason, presumably otherwise they would not be certified as N95 (FFP2). My understanding is that "spewing" is negligible compared to the issue of heating and excess moisture buildup in a valveless mask (particularly in hot summer). Any custom modification of a N95 mask may breach its integrity and resistance. Brandmeister^talk 08:19, 3 September 2020 (UTC)[reply]

For (2), the comparison does not make much sense. Toilet paper shortages were due to (a) panic buying resulting in a build-up of stock among consumers, (b) a change in the products consumed (toilet paper bought by companies, theaters etc. is not the same product as bought by private individuals). (a) takes care of itself within a few weeks because the demand spike is followed by a demand gap, (b) can be fixed by a (supposedly easy) retooling of existing machinery. On the other hand, the demand for masks has increased dramatically since February/March and will remain at a higher-than-before level for quite some time; it is not easy to expand production ten-fold at short notice, even with big price incentives. Tigraan^{Click here to contact me} 08:45, 3 September 2020 (UTC)[reply]
Most studies indicate such valved masks are not terrible in spreading the virus, as long as the valves are properly used. This is just one example of many articles on the subject. The valved mask is not as good as the full N-95, but it is, within error bars, comparable to, and in some cases better than, things like cotton masks and surgical masks. In short: The valved mask is not as good as the full N-95, but neither does it "spew virus", and it is comparable to the wide range of other kinds of masks on the market, and much better than things like bandanas and T-shirt material buffs. If you can't get the fitted N-95, the valved one may be among your next best options. --Jayron 32 11:47, 3 September 2020 (UTC)[reply]

Why is surgery done with only surgical masks? Sagittarian Milky Way (talk) 15:57, 3 September 2020 (UTC)[reply]

Sometimes they also use surgical knives. --Lambiam 21:13, 3 September 2020 (UTC)[reply]

It gets worse, i've heard some rogues even wear surgical gloves! Zindor (talk) 21:46, 3 September 2020 (UTC)[reply]

Some of them also wear surgical stockings. {The poster formerly known as 87.81.230.195} 2.122.2.158 (talk) 22:49, 3 September 2020 (UTC)[reply]

So why is it okay to do surgery with only a fancy cloth on your face but corona nurses need gas mask-looking things? Sagittarian Milky Way (talk) 01:49, 4 September 2020 (UTC)[reply]

I suspect your premise is flawed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:50, 4 September 2020 (UTC)[reply]

It looks like a serious question. Face masks during the COVID-19 pandemic is a good start to learn about the various masks. Medical prophylactic practices have to strike a balance between efficiency (protection against contamination by a given pathogen), cost, and side effects (a hazmat suit will block all pathogens, but it would be unwieldy to perform chirurgy from inside one); it is not surprising that the best option for a given context might not be best for another context. You should also note that handling yourself around an operating room requires nontrivial training ("operating room training" returns a bazillion hits for certification programs), so it seems possible to me (OR warning) that stringent procedures compensate for lower-protection equipment. Tigraan^{Click here to contact me} 15:22, 4 September 2020 (UTC)[reply]

Chemistry, Nitrogen and it's compounds form three[edit]

How is nitrogen gas prepared ? — Preceding unsigned comment added by Emmanuel ngetich (talk • contribs) 17:58, 3 September 2020 (UTC)[reply]

Mostly by taking it from the air, of which it is the overwhelmingly major constituent. The air separation article describes the major processes for doing it. DMacks (talk) 18:08, 3 September 2020 (UTC)[reply]

Though, pertaining to the section title, nitrogen compounds are rarely if ever prepared from nitrogen gas, because the dinitrogen triple bond is very strong and takes a lot of energy to break apart. Instead, ammonia or other nitrogen compounds are used as the nitrogen source. Ammonia is produced today with the Haber–Bosch process, one of the most important inventions of the 20th century and a major industrial process. --47.146.63.87 (talk) 22:14, 3 September 2020 (UTC)[reply]

Which of course it is important to note that the Haber-Bosch process uses nitrogen derived from the air as it's feedstock, so ultimately most industrially-derived sources of nitrogen compounds do indeed come from nitrogen in the air. Before the Haber-Bosch process, nitrogenous compounds were primarily obtains through old-fashioned biosynthetic means: we used plants and animals to produce them, and we got it from there. This includes things like guano deposits (basically bird shit and bat shit) and nitrogen-fixing microorganisms in the soil and plant roots known as Diazotrophs. Bird shit used to be so important to the world economy that global conflicts have been started over access to it. See Guano Islands Act, Chincha Islands War, War of the Pacific, etc. all of which were significantly about control of guano. The Haber-Bosch process changed a lot of that. --Jayron 32 15:22, 4 September 2020 (UTC)[reply]

Right, Haber–Bosch catalyzes the breaking of the dinitrogen bond so it can be done at scale. Non-synthetic nitrogen compounds get their nitrogen ultimately from nitrogen fixation by microbes, which have nitrogenase enzymes that accomplish the same trick. --47.146.63.87 (talk) 02:11, 5 September 2020 (UTC)[reply]