With the spread of Covid-19 around the world and heightening cases continuously, there are multiple aspects of the worldwide pandemic that need our attention. Not only knowing the difference between an epidemic and plague, the signs and symptoms of Covid-19, we also need to be attentive towards the needs of our hospital workers to help save patients. There are a lot of terms to learn. When the Coronavirus was at its worst, you've probably heard that hospitals needed more ventilators, N95 respirators and surgical masks.
N95 masks are so-called because they are a U.S. standard that requires masks to filter out at least 95% of microscopic particles, including droplets containing the Coronavirus.
What Does N95 stand for?
The "N" in N95 stands for "Not resistant to oil-based aerosols such as lubricants and cutting fluids,". Following it "95" represents the respirator's efficiency when tested with an aerosol
having a mass mean aerodynamic diameter of about 0.3 micrometres. It is the most penetrating particle size range for most filters. Unless you are getting exposed to oils, the N-series will do just fine for you.
An N95 is classified as a respirator and not like a surgical mask in the United States. The National Institute for Occupational Safety and Health or NIOSH, for short, certify these respirators, so you remember anything from here, know that a NIOSH certification means we have a respirator, not a surgical mask. The FDA approves surgical masks (The Food and Drug Administration).
What's the Mechanism behind N95?
Before beginning, let's all agree, before March 2020 it's a good chance that many of you didn't know what N95 masks were or at least didn't think about them unless you were doing some home repair project with lots of dust or live in a part of the world with crazy pollution or wildfire smoke.
Learning about them, one might think that an N95 mask is a very delicate strainer: a mess of fibres with gaps too small for dust and other airborne particles to get through. Strainer filters are out particles more massive than their openings and not particles smaller than it's openings. So you would expect that after a certain point, small enough particles will sneak through. But this isn't how N95 masks work: the particles it filters are generally much smaller than the gaps between the fibres in the mask! Additionally, the N95 mask is amazingly good at filtering both the most extensive and smallest small particles. It's medium size small particles that are hardest for it to block. The overarching goal of an N95 mask is instead to get airborne particles to touch a fibre in the mask. Regardless of how big an air particle is, it stays stuck to it once it feels a fibre and doesn't become airborne again. It isn't anything special about the fibres, but about the size of the particles. Everything is sticky at a microscopic scale because the attractive weekly force between or the Van Der Waals force between molecules is strong enough to hold tiny little things in place. So it would help if you didn't think of an N95 mask like a fine window screen that keeps insects of a specific size out. You should think of them more like a sticky spider web that can catch an insect of any size as long as it touches a strand.
And so N95 masks utilize a lot of different levels of physics and mechanical tricks to get particles to touch their fibre.
First, many spider nettings are better than one. More layers of sticky fibres result in more chances for particles to get stuck. And how probably particles are to hit or skip a fibre depends in large part on their size. Airborne particles are more massive than 1000th of millimetre travel in straight lines because of their inertia.
The presence of so many layers of fibres and the straight-line paths followed, are virtually guaranteed to hit a fibre and eventually stick to it. As mentioned earlier, particles of the in-between sizes are the hardest to filter. But N95 masks can attract particles of all sizes to them using an electric field. In the presence of an electric field, even neutral particles develop an internal electrical imbalance drawing them to the field's source. An N95 masks electric field isn't just ordinary static electricity. Their fibres are like permanent magnets but for electricity: electrets! Just like you can permanently magnetize a piece of iron by putting it in a strong enough magnetic field. A part of plastic can be electrified to give it a permanent electric field. After all, this is the point of an N95 mask to filter out particles from the air. Dust, smoke, pollen, bacteria and viruses all have different sizes and are filtered by N95 masks to different extents.
Facing the Global Shortage Efficiently
N95 masks are intended to be disposable, but the demand from Covid-19 has led to a global shortage of N95 masks, and the reality is that health workers have to reuse them and thus decontaminate them. It's essential to be aware those certain kinds of decontamination methods:
For example, using alcohol or liquids can damage the electrostatic properties and destroy the filtering even if the mask appears not so affected. A volunteer team of scientists develops and shares research-based decontamination methods so that masks can be reused during this crisis. For substantial development, we need to follow the technique of decontaminating in which the quality remains intact.