口罩能保护人们远离冠状病毒吗?

Can homemade DIY and surgical masks protect against the coronavirus

随着2020年初,冠状病毒在中国的爆发,数百万人不得不在一夜之间成为口罩专家。

但是,口罩种类很多,哪些口罩可以保护我们免受病毒感染?口罩能过滤冠状病毒吗?我们需要使用N95口罩来保护自己免受冠状病毒等病毒的感染吗?

Quora上有这样一个问题:口罩能避免我们感染上冠状病毒吗?

戴口罩可以避免人们感染冠状病毒吗 

幸运的是,科学家已经积累了能够回答这些问题的可靠数据。

冠状病毒颗粒有多大?

 

冠状病毒的病毒粒子(或颗粒”)是直径约125纳米(0.125微米)的球形颗粒。最小的颗粒是0.06微米,最大的是0.14微米。

冠状病毒病毒颗粒多大

 

这意味着冠状病毒颗粒比PM2.5颗粒小,但比一些灰尘颗粒和气体大。

 与其他污染类型相比,冠状病毒的颗粒大小

 

现在我们知道冠状病毒颗粒有多大了,口罩能过滤掉这些颗粒吗?

让我们把这个问题分解成两个更简单的问题。

  

1.防空气污染的口罩能捕捉到冠状病毒颗粒吗?

怀疑派说:

冠状病毒(以及其他病毒)非常微小——比人类头发的直径小500倍。

况且,“口罩那么薄,他们怎么可能阻挡得了那些微小的冠状病毒颗粒呢?

但是

科学的测试告诉我们:

爱丁堡大学的研究人员测试了不同种类的常用口罩他们用了柴油发电机来模拟汽车排气装置,向不同口罩排放废气,然后用一个粒子计数器测出有多少颗粒穿透了口罩。

测试口罩是否可以过滤冠状病毒颗粒

一个重要的细节:他们使用的粒子计数器能够测量到0.007微米的颗粒。所以我们现在讨论的真的是微小颗粒!

他们测试了一系列口罩,他们的发现:

戴口罩可以过滤冠状病毒颗粒

3M的口罩能够捕捉到95%以上的微粒,而微粒的厚度只有0.007微米,这比冠状病毒小十倍。

有些人可能会感到惊讶的是,外科口罩也能够捕捉到80%的微小颗粒。

口罩的测试告诉我们:口罩(包括外科医用口罩和N95口罩)可以捕获比冠状病毒小10倍以上的微小颗粒。

即使是非常微小的颗粒,口罩也能过滤掉。

好,那我们继续进入下一个问题。

2. “好吧,口罩可以捕捉比冠状病毒更小的微粒,但如果空气从口罩边缘溜进去呢?”

怀疑派说:

“理论上口罩是管用的,但是这些测试不是在真人脸上做的。所以,当你戴的口罩不能和你的脸完美贴合时,它们还是没用。”

科学的测试告诉我们:

这个问题更难回答,因为你必须在真的戴着口罩的时候测试效果,而且,想要做的这一点,你需要一个非常昂贵的密封性测试仪器

幸运的是,我们的确在这样一个昂贵且可靠的机器上做了很多关于口罩的测试

口罩密封性测试 Smart Air聪明空气实验

蓝色的管子采集口罩外的空气,白色的管子从口罩内采集空气(密封测试细节)。

Smart Air 聪明空气的创始人Anna,和生活在北京的Dr. Richard Saint Cyr做了口罩密封测试所以我把我们三人的数据整理了一下。

这是不同口罩在我们脸上的密封效果:

不同口罩的密封效果

点击可查看完整的测试数据

一些3M口罩甚至能捕捉到超过99%的0.01微米微粒(比冠状病毒小10倍)。更重要的是,外科手术的口罩也特别有效,捕获了63%的微小病毒大小的颗粒。

阅读更多:戴口罩可以保护身体健康

最后,回到现在大家最关心的话题上:

口罩能保护我们远离2020新型冠状病毒吗?

看完文章,大家一定发现了,口罩可以过滤掉哪怕是最小的颗粒——比病毒小10倍的颗粒。更重要的是,我们也测试了佩戴上口罩后的实际效果,是非常好的。

另外一个大家都很关心的,就是医用的便宜口罩到底有没有用。不用担心,它们在过滤病毒大小的颗粒时,效果也是非常棒!

Smart Air会携科学数据,与你一起度过这些日子。

 

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David Caloca

Hi
I find this very interesting. I think you should also consider the fact that the virus is transmited mostly throughout the Flugge droplets, which are droplets produced by humans by coughing or sneezing, wich measure to 0.5 mcm to 10 mcm.

– Epidemiology of Respiratory Infections. https://link.springer.com/chapter/10.1007/978-3-030-26961-6_28
– Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease-2019 (COVID-19): The epidemic and the challenges. https://www.sciencedirect.com/science/article/pii/S0924857920300674

Richard Baker

I am a old army medic, now a retired RN. Want to help others and thinking out of the box by making DIY face masks for shelters that have no supplies. Putting a mask on persons with symptoms. Will layers from hippa furnace filters be useful material to capture virus? Any other ideas?

Liz - Smart Air

Hi Richard, I’m really glad to read all those comments offering DIY masks for your local hospitals! We are working on more tests in the following week and will publish the results as soon as possible! Stay tuned!

Enzo

The science doesn’t base itself upon a single or a couple of studies.
A sistematic review outcome is that there is no evidence that the mask are useful. The same things says WHO. If a mask filter a particle, this doesn’t mean that protect you…
https://www.cambridge.org/core/journals/epidemiology-and-infection/article/face-masks-to-prevent-transmission-of-influenza-virus-a-systematic-review/64D368496EBDE0AFCC6639CCC9D8BC05

Yaman

Have you even read your own reference? It says right there in the summary “Further studies … are required to better define the effectiveness of face masks …” This is one of those further studies. What is the problem?

SIMONE LOPES DE MATTOS

Please,
I am writing a PhD thesis in Engineering and I need scientific references on the interception of particles smaller than 0.3μm in the N95 filter mesh.
You can provide me with references of scientific articles.
I would be very grateful
[email protected]

Kelly

I’m curious what happens when you use a mask like this many times? It’s impossible to buy a stack for several months.

Does the filtering capacity stay the same? Is it ok as long as you wash your hands after touching the mask? And what about indirect contact? For example you touch the mask, then touch your head, arm, clothes whatever. You wash your hands, but then touch the same spot again, then touch your eyes/nose/mouth/optional vagina. What then? (and yes I realize this is probably way out of your area of knowledge).

Liz - Smart Air

Hi, Kelly, we have tested masks that have been used for 30 days, then link to the data: https://smartairfilters.com/en/blog/how-long-air-pollution-masks-last-lifespan-data/
About indirect contact, I just try to wash my hands the first thing after going back home, then deal with the clothes and masks, and wash my hands again.