雾霾天，戴口罩真的有用吗？

《雾霾天，戴口罩真的有用吗？》有53条评论

1. It’s confusing, there are two 3M9001V in your table, which differ in results (the efficiency) greatly. Which data is true for 3M9001V?

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   • Hi yuan. Song here. Thanks for reading. Those are based on the fit tests on different people.

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2. I have noticed that parts of my skin that is covered by clothing doesn’t get dirty as quickly as skin that is exposed. When I rub off dead skin the exposed skin has a darker color than the covered skin. Skin can be washed but that is not the case for lungs. It’s sickening to think about how much dust that I dust that I have inhaled in my life. I wonder how much human activity has contributed to particulates.

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3. This is a really informative knowledge, Thanks for posting this informative Information. Surgical Face Masks looking very nice.

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4. How about time in the mask. Even surgeons rotate in surgery and put on fresh ppe. The average store visit is 30 minutes to two hours. After the mask is worn for 30 minutes, what’s the “escape” amount specifically during the time after 30 minutes. I ask because I have been questioning the logic of employees wearing the same mask for hours on end.

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5. What is that cotton mask in the last? Is that a cotton mask with PM2.5 filter inside(Eg: Pureme replaceable filter mask) or just a cotton cloth mask without any filter?

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   • Hi Naveen, Liz here. The cotton handkerchief is something you can get online, typically a thin layer of cotton fabric with great breathability. So there’s no filter inside.

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     • Hi, first of all thank you for this informative article. I think Naveen meant the LVDun mask that’s last (far right) on the bar chart, because I had the same question. I noticed this type of mask is sold with the removable filter sheets. Do you know if the mask in the study had the PM2.5 filter in place or was just the mask alone?

       Also, were the prices in the Effectiveness vs. Price chart adjusted for the number of uses you can get per mask? It would be kind of silly to compare the cheap price of a disposable one-time-use mask to the expensive price of, say, the reusable fabric vog mask, without accounting for how many times the reusable one can be washed and reused.

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6. Thank you for this article, and for https://smartairfilters.com/en/blog/kids-air-pollution-masks-work-effective/

   I’m curious about methods of custom-fitting masks to your face. Some silicone amalgamating tape might be added to masks like a bias-tape binding, with and extra layer added where needed. Custom-shape swimmers’ earplugs use two-part curing silicone and low-temperature thermoform plastic (warning: construction silicone sealant, while curing, releases acetic acid, which can hurt your skin and make you allergic to vinegar). Could you test and suggest some techniques for those of use with odd-shaped faces, including kids?

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7. Interesting. I went and looked up bicycle masks on Amazon. Not terribly expensive and probably provide protection on INHALE, but they all see to have one-way valves for when you EXHALE, sending your breath directly out, defeating at least half the purpose of wearing a mask…..

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8. Are these masks reusable and what do you think of using hand kerchief and how well it is going to protect us from the virus

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9. Morning I am from South Africa , Please advise me if a Pleated dust Mask is the same as a surgical mask? and if not is it effective against filtering the virus. There are of course a lot of profiteers in Africa selling masks I have just been offered some from China which I would like to donate to rural clinics in my area as the HIV and TB in our country leaves these patients with not much resistance to any virus.

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   • Hi Rose. Liz here. Greeting from our Beijing office! Masks, even surgical masks have different grades and filtration rates. The safest way is to ask your supplier for a test certificate to make sure your masks can meet the needs. For your reference, here is the article on mask ratings: https://smartairfilters.com/en/blog/comparison-mask-standards-rating-effectiveness/

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10. What about the KN95 masks?

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    • Hi Gordon, Liz here from Smart Air. Read about mask ratings here: https://smartairfilters.com/en/blog/comparison-mask-standards-rating-effectiveness/

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11. I just want to know where I can purchase the 3M Respirators…I found the surgical ones on the 3M website many good protective products but there is no way to purchase from the website, it’s crazy, I’m not able to order anything there is no order form on the site. I live with my 93 year old mother and I just want to male sure I’m not bringing anything home to her, so looking for a medical grade respirator/mask, such as the N95. Any help on where or how to purchase would be great!

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    • I do not know where you live, but in the USA your first stop might be AMAZON.com. Alternately, use Google, look for the kind of mask you want, and then use their shopping option. Back at the very beginning, I got a 3M respirator that was only about $15, but you had to order 2 N95 or better filter cartridges for around $7 each. There are other choices that come with air filters. Originally Amazon had a large selection, and you could also search for a mask, e.g., “3M model XYZ123” and “price” to find the same item being offered by various vendors. I think there is growing availability of N95 level masks. Filter cartridges last until they get too clogged up to be comfortable to breathe through.

      I bought some KN95 “disposable” masks via Amazon. They looked good, but when I held the edges down to eliminate leaks they became too difficult to breathe through. I have read that many KN95 masks sold in the USA do not filter up to their alleged rating, i.e., they are faking if they claim N95 or the approximately equal KN95 status.

      Unless you want to do a great deal or research, you are probably better off choosing 3M or some of the masks made by major USA (or Canadian, GB, etc.) firms. Some use designations other then the Nxx standards used by 3M, and you’ll just have to research how they stack up against each other.

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12. I was looking at buying kn2.5 disposable filters for use in reusable home made face masks. Are these effective for corona virus protection? What ffp rating would they have? Lastly I work in a Joinery with a lot of sawdust. Would they be effective in that type of environment?

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    • Hi John, regarding to mask ratings and their filtration performance, read this article: https://smartairfilters.com/en/blog/comparison-mask-standards-rating-effectiveness/

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    • I suggest you look for “filti” nanofiber fabric “blankets” that you can cut to size. Filti.com has products that I think can be trusted. At least you have a known firm that has to be careful of US laws about things like claims on filtering ability. Some KN95 stuff is genuine, and KN95 doesn’t differ significantly from N95. But even the stuff that operates at N95 levels can be difficult to breathe through. It’s expensive to buy a package only to discover that the product doesn’t meet your needs.

      Any of these masks, even those that don’t really reach N95 levels of efficiency, will take care of sawdust.

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13. Are the pollution masks you tested with filters? Because I’ve seen some sellers claim to sell them with KN99 replaceable filters?, is that possible? And if they come with KN99 filters shouldn’t be a pretty similar to the 3M disposable masks?
    Thank you in advance!

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    • Hi Chris, Liz here. The N95 masks we tested in this article doesn’t have a replaceable filter. We haven’t tested any masks with a removable filter yet, so I’m not sure about the answer.

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14. If you’re like me and cant find any masks. Try getting the A/C filters that block viruses. Cut away all of the metal and cardboard . Cut the filter in 4×4 pieces. Line a bandanna with it and just make sure you have a tight fit.

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    • becarefull the have fiber glass in most of them

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      • George please stop spreading this rumor, you are not stating facts and stopping people from using an available material for mask filter.
        There are 2 types of furnace filters: Fiberglass and Pleated. MERV 1-4 are spun fiberglass and are not good at trapping any particles, they are more for keeping spiders and socks from being sucked in your furnace motor. MERV 5-20 are pleated filters and are made from paper or in the higher efficiency ratings cotton/polypropylene fibers. I would suggest a MERV 13-20 because these are usually the cotton/polypropylene material. If you call the manufacture of whatever brand you buy they are required to supply an MSDS or material data sheet which list all materials used in the making of their product. This will ensure there is no “fiber glass” in the product. What I will be wearing when I go out is a home made mask of 2 layers of cotton/polyester fabric with a MERV 13 A/C filter material in between. Also, a HEPA vacuum bag can be used for making filter and no they don’t contain fiber glass either. Please do your research and most of all be safe!

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      • Some manufacturers have put out notifications warning against the “off-label” use of some of their filters. It’s best to know what any filter you choose is made of. Just remember that when manufacturers make stuff to hold dust, etc. from your vacuum cleaner, or to filter out dust bunnies from your HVAC system, they probably weren’t thinking about how people might use them for other purposes.

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    • Save yourself effort and frustration. 3M has a “filtrete” blanket-type filter. (They identify it as being suitable for “Hammock” type furnace filter holders.) The MERV rating isn’t as high as the Filti brand (Filti.com), but 3M is a recognized firm and if they say the filter material is MERV-12 (or whatever they say it is — look it up online), then that is what you will get. It’s apparently the same stuff that they glue to the expanded metal sheets you are having to deal with.

      Finding these blanket-type filters on-line is a little difficult, but a few months ago when I bought a sheet of it, it didn’t take me that long to locate a supplier.

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15. Did you test Cambridge masks, too ?

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    • hi Lucy, Liz here. We haven’t tested a Cambridge mask yet. We know there’s a huge demand for reliable, science-backed data right now, so we’ve created a campaign to gather information on what our readers wants to test. To vote on what test you expect to see and support our campaign, visit our Fundly.com page here: https://fundly.com/best-diy-mask-materials

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16. Can masks made with coffee filters double lined help? How do they compare with N95 masks?

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    • Hey Charlene, we’re working on testing coffee filters and should have a follow-up article out soon!

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17. Thank you for this thorough post and data. It’s been the most informative out of the 10 articles I just read through on effectiveness of masks.

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18. Hi Thomas and Team,

    Thank you for sharing this interesting data.

    Could you share the specs of the surgical mask you used in your study please? It is the most accessible mask for the general population and there are many different types (e.g. 2ply vs 3ply, BFE vs PFE vs VFE). Many westerners just do not believe they are useful at all for tackling the spread of / preventing catching coronavirus. Your sharing of the specs of the surgical mask used would help clearing the uncertainty that many have.

    Many thanks!

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    • Great question Heidi! The surgical mask tested in these experiments was a ‘Weijian’ (稳健) surgical mask. It meets the YY0469 Chinese standard for surgical masks. This standard requires a BFE (Bacterial Filtration Efficiency, for particles 3.0 microns) above 95%, and a PFE (Particle Filtration Efficiency, for particles 0.1 microns) above 30%. Here’s the actual standards (written in Chinese):
      

      This certification requirement (a requirement to capture just 30% of particles 0.1 microns in size) is actually much lower than many of the international or US standards (for example the ASTM F2100 Level 1, Level 2 and Level 3). Most surgical masks in the US require a PFE of 95% and above. Here are the ASTM F2100 standards:

      

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      • Hi Paddy,

        Thank you very much for your reply!

        Indeed, the US, together with Japan and Korea, probably have the most stringent requirements. On the other hands, the EU standard EN:14683 only specify BFE but no PFE, even though it is similar to ASTM F2100 as claimed by Nelson’s lab (https://www.nelsonlabs.com/en14683-harmonizes-bacterial-filtration-efficiency-and-differential-pressure-with-astm-f2100/). I am based in Europe hence my interested in the specs of your masks 🙂

        One more question, are specs of the surgical masks tested here the same as the one from this experiment of yours (https://smartairfilters.com/en/blog/coronavirus-pollution-masks-n95-surgical-mask/?fbclid=IwAR0d3W-g6zl_G9cRygwCYt2J2PAfYYzg1cV9toacjwn6WBTt_mFqbyB1ikE)?

        Many thanks!

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        • No problem Heidi, I’m glad the data and info is useful to you! Yes, the specs of the surgical mask tested in that 2nd article you link to are the same. They’re all part of the same fit-test experiment undertaken by Smart Air and Dr Richard Cyr (a doctor in Beijing). Here’s a link to his original test results where he gives the specifications of all the masks. ‘Weijian’ is the surgical mask brand: http://www.myhealthbeijing.com/children/my-personal-fit-testing-heres-the-best-pollution-mask-for-me/

          

        • Hi Paddy,

          Thank you so much.
          Probably my last question: are you guys intending to publish this data in any journal articles? More specifically, I am talking about the part about different filtration efficiency of 0.01-1 micron particles among the masks you have tested.

          Many thanks,
          Heidi

        • Great question. You have a better dataset than the review article that came out on May 1st. https://gh.bmj.com/content/5/5/e002553

      • So do we look at BFE or PFE? Is the higher PFE necessary? If their test says 30% why are you saying it’s closer to 80%? If this were true why would most experts claim masks don’t do anything? It doesn’t make any sense. Maybe you are missing something.

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19. Can you share how long each of the masks in your test last? I hear the cheaper 3M masks, whilst they are very effective, can only be used once.

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    • Hey Dion, we’ve actually done these tests. We’ve tested an 11 day old mask to see if it lasts, as well as a 20 and 30 day old masks to see if they are still effective. Check out those posts for more information!

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20. Hey Thomas & team,

    Richard Saint Cyr says, “The other major issue here is fit: even a small amount of air leaking around the corners makes any mask basically worthless.”
    http://www.myhealthbeijing.com/children/pollution-masks-children-n95/

    It sounds like you disagree, and you’re saying that even with small air leaks, a good mask is still probably cutting out a decent amount (say 50%) of pollution. Is that right?

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    • Hey Sam, Paddy here – I’ll reply on behalf of Thomas as he’s out running nerdy tests right now! It’s true that even if a mask doesn’t fit 100%, it’ll still be doing something to reduce air pollution. One great example is the surgical mask data in this article. You’ll see how in the fit test it managed to capture 63% of PM2.5. That’s great for a mask which is so ‘leaky’! In practice other masks are much much better sealed than surgical masks, so I think you can expect to get very high filter rates. Most of the masks we tested (see the graph above) got over 90% effectiveness.

      I do recommend you check out our quick guide to making sure your mask fits properly, just so you’re not missing out on anything!

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21. Thanks for the awesome blog, pls keep writing

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22. Thank you so much for such thorough investigation! I have been using a 3M 9211 as I am cycling around Los Angeles for more than a year and I can definitely say that they are effective. I have two questions that I can not find the answer anywhere! How often is recommended to change the mask? Also, although I can not smell car exhaustions (vs not wearing it) I can definitely smell tobacco (or weed, it’s LA you see) when I am stopped at the traffic light and a pedestrian passes by smoking. The smell is clean so does that mean that aromatic cyclic compounds are not filtered?

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    • Glad you’ve found the data useful Vangelis! We had exactly the same question on how long you can use your mask. That’s why Smart Air nerd also tested a 14 day old mask during his fit tests. You can find the data in our mask lifespan writeup. As for your second question: this data shows that masks are great at capturing PM (particulate matter), but that says nothing about how well they capture gases. Smells, formaldehyde, ozone and more all fall into that category, and your typical 3M masks can’t capture these gases. There are some ‘carbon’ or ‘charcoal’ masks on the market, which may help with filtering out gases (carbon is great at capturing gases). You could pick some up and try them out – if the smell goes then you’ll know they’re working!

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23. I started wearing a 3M 7502 (7500 Series) respirator. I have two pratical options available plus a super safe one.
    1) with the 2097 filter (P100 filter class plus carbon). Advantage: filter class highest. Or
    2) the 6001 CN (carbon filter) plus the 5N11 CN (N95 filter class). Advantage: easier to breathe and huge carbon filter.
    3) There’s also the possibility to combine the 6001 with the 2097 but its quite heavy and hard to breathe. Advantage highest particulate filter class plus big carbon filter. Disadvantage: no sports, e.g. riding bike, comfortably possible.

    What do you think about that?

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    • I forgot to mention that the best advantage of the 3M 7500 respirators over the foldable 9332 is the fit. There is absolutely no air passing the face seal.

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24. It does seem likely that particles in masks will work their way loose under suction at some point and be inhaled. What would prevent this? Is there gluey stuff in the masks? Does the testing you speak of test this?

    In fact, the instructions for my surgical mask say to wear the mask once only, suggesting another issue.

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25. Hello, also the leak is more predictable on the exhale time than on inhale time due to a suction phenomenon right ?

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    • Some masks are actually designed to ‘leak’ air out the sides when you breath out. You are right that when you inhale the mask should ‘suck’ and stick to your face, so there should be no leaks.

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26. I am writing from Delhi and I have used a Vogmask which according to the above data is 95% effective.
    This may be true but I have two comments:
    a) for my face, even the largest Vogmask available does not come below my chin (I have a big nose & big face!)
    b) when I am wearing my Vogmask and spectacles together, the spectacles fog over – meaning some of my exhaled air is reaching the glass of the specs.
    I would conclude that the fit of the mask around the bridge of my nose is not effective and that it may not prevent me from directly inhaling polluted air.
    How does this square with the 95% effectiveness claimed above?
    I think a tight-fitting N95 mask may be superior to a relatively loose N99 mask – but I cannot prove this.

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    • Good points Vikram, which mask works best for who always comes down to how well it fits on your face. Masks might use a reliable and effective filter material, but if it does not fit, it may not work. That’s why making sure you get a mask that first your face is most important. If you feel like the Vogmask doesn’t give a good fit, then you should consider another mask. Having said that, when breathing out it’s normal for air to leak *out* round the edges. Just when you’re breathing in there shouldn’t be any air breathing out.

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