How do N95 masks protect us? Can I just wear the typical surgical mask?

With the reported high number of infected COVID-19 cases around the globe, a high demand on personal protective equipment (PPE) is expected. Among these PPEs, the N95 masks have been the latest and hottest item in the market.

What is N95 masks then? What is the difference of this mask from the typical face/surgical masks we usually see? Let’s have a brief discussion.

The first question is, what is N in N95 and what does 95 mean?

A dude thinking of the meaning of N in N95.

Okay. So hear me out. There is a division in the Centers for Disease Control (CDC), known as National Institute for Occupational Safety and Health (NIOSH), which sets out rules for all particulate filtering respirators. In short, all manufacturers who plan to make respirators intended for public safety, must comply to the rules of NIOSH. The rules basically aim to remove hazardous particles from the air.

So going back to the question, N stands for “not resistant” and 95 means “filters 95% of the airborne particles”. Hmm, a bit tricky right? Not resistant to what? The respirator should not be resistant to oil. Why oil? This is primarily intended for industrial environments. The oil aerosols, when trapped in the respirator, can degrade the efficiency of the filter. Yes, these oils make your masks ineffective because (let’s be a bit scientific here) the electrostatic charges between filter layers that serve as a magnet in trapping airborne particles, are slowly being removed. Without these charges, anything can just pass through the holes of your mask.

Oh, and the number attached to it? It pertains to the percentage of airborne particles that can be filtered. For N95, it means that 95% of the airborne particles can be filtered. With this in mind, this also tells us that filtration is not 100%. You might be thinking right now, “then why use this?”. Actually, there are still other masks which are higher in terms of filtration efficiency. For instance, we have N99 (filters 99%) and N100 (filters 99.97%). As you may notice, there is no such thing as 100% because our surroundings are filled with hodgepodge of everything. For our current scenario (COVID-19), N95 masks are reasonable. What we are really after is the size of the pores or holes of the mask. The company 3M mentioned that their N95 masks has holes with a size of 0.3 microns. This means that those particles above 0.3 microns can be filtered out.

How small is a micron?

One meter is 1000000 micrometers.

Now you can imagine how small a micron is. The size of the COVID-19 virus is approximately 125 nanometers (or 0.000000125 meters). So what do you think? Is N95 sufficient? The answer is… unfortunately NO. The holes of the mask are bigger than the size of the virus per se. The Covid-19 particle is indeed around 0.1 microns in size, but it is always attached to something larger. According to Professor Linsey Marr (and I will quote it here (thanks to, “There is never a naked virus floating in the air or released by people”. This means that the virus attaches to water droplets or aerosols that are generated when we breathe, cough, sneeze or talk. And that what makes the virus larger than the hole of the mask. Hmmm.. convinced yet?

Another thing is that, N95 mask essentially operates on the principle of electrostatic attraction. This means that particles are attracted/drawn to the fiber and are therefore trapped. Yup, trapped in those holes. This what sets the N95 mask apart from other face masks. This is also the reason why it is not recommended to reuse N95 masks.

So yes, N95 masks work! πŸ™‚

But can we just use the typical face mask in this time of pandemic? The answer is YES and NO (but not advisable). Okay, remember we are talking about viruses/bacteria and that the size of the holes of the mask is very much essential. Researchers found out that the typical surgical masks provide low protection against aerosolized infectious agents (Balazy et al. 2006). Again, we are talking about very minute particles, even smaller than the period you see at the end of this sentence. The researchers also highlighted that surgical masks are primarily designed to protect the environment from the wearer, whereas the respirators (e.g., N95) are supposed to protect the wearer from the environment. Oh, I also mentioned that face mask can still be considered (but not advisable). How? Others suggested that you can place tissue paper (few squares) inside your face mask, mimicking the filter of a respirator. But then again, we are not sure if this will really protect you. Remember, at this pandemic time, it is a matter of life and death. So as much as possible, wear the proper PPE. Okidoks? πŸ™‚

Oh, please also remember, DO NOT HOARD masks. We have a lot of FRONTLINERS who need the respirators more than we do (I meant “we” or those individuals staying at home and not always exposed to these infectious particles). Please be kind, responsible and reasonable.

Adios! Stay safe guys!

Reference: Balazy A, Toivola M, Adhikari A, Sivasubramani SK, Reponen T, Grinshpun SA. 2006. Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? Am J Infect Control 34(2):51-57.


    1. Hello there sir! 😊 Thanks for pointing that out. Appreciate it. I have made revisions on that post. (I’ll be very careful with the facts I will be writing in the future). Thanks so much! Means a lot to me specially that I am now considering to post more frequently this year. Happy New Year! πŸ₯³


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