i Do I need a respirator or facemask against Coronavirus? – Daniel's Blog

Do I need a respirator or facemask against Coronavirus?


WTF does an IT techie know about respiratory protection?

First of all I have a warm and fuzzy knowledge about this thing as my father worked in the personal protection equipment industry, supplying to several major fire services, power stations and oil refineries, so I have picked up some knowledge and stories, and one of those is that there are a metric sh*t-ton of different types of protection and standards out there, so it’s worth doing some detailed research before going on eBay and buying the cheapest mask available.

Second and (literally) more closer to home, I did a lot of that (google based) research due to some renovation work on my own house, where I needed to use a couple of gallons of some quite nasty, highly volatile and generally disagreeable chemicals to remove glue remains from synthetic tiles on the entire ground floor.

So, knowing that I did not know what was best, I thought a quick google would be enough, and this led down a looooong rabbit hole.

So, which one do I need?

  • If you are not sick, and you don’t know anyone who is sick, none really.
  • If you are ill and need to go out, then a plain, simple surgical mask to protect everyone else from you will be enough.
  • If you are around people that are sick, then any mask matching N95, N100, FFP2 or FFP3 will do – and keep your distance!
As seen in the London Underground
As seen in March in the London Underground….

If for any reason you do need to wear a mask, remember to install it as well as you can, then avoid touching it. Every time you remove your mask, throw it away and obsessively wash your hands, and never re-use a disposable mask one removed!

So, that is the very short version. Want some technical details, lets go for a very quick trip down a very long rabbit hole, about disposable and “non”-disposable filters.

Disposable filters

Surgical or non-surgical?

Non-surgical respirators are standard particle and vapour filters, depending on their design and category. They may have an out vent installed to allow air to be exhaled easily, though masks with an out vent will not stop you from exhaling particles if you are infected.

Surgical certified respirators do not have an out vent as described in the “surgical mask” section below, you don’t want a direct unfiltered path from your mouth to the outside world via that vent, and it’s also a risk point as this is a possible source of ingress of fluids projected under pressure (think: blood).

Surgical Masks – Filters most particles down to 5 microns

surgical mask

Thin single-use paper masks, actually designed to stop you spitting or coughing droplets into a sterile “field”, like someone on an operating table. It will help of you have a cold and don’t want to spread your coughed droplets containing virus particles on people around you, but it’s not a fitted mask, it does not seal around then face, so nothing to stop air being sucked in through the sides.

guy sneezing
If you are sick and sneeze, this actually happens…. unless you have a paper mask as a barrier.

Pollution filters – Filters most particles down to 2.5 microns

pollution filter

These are re-usable and washable, generally made out of some flexible fabric or neoprene sheet. It may or may not have an out vent, it may or may not have an active carbon filter. They are designed to filter out particulate from air pollution breathing in, and may have a direct vent to ease breathing out.

These masks are not guaranteed medical standards, but will be an efficient large particle dust filter. If it has an out valve, then it won’t stop you coughing out infected droplets if you are sick as they will go through the valve, bypassing the filter.

Some come with replaceable filters, and I have seen one for sale that says “0.3 to 10 filtration”. That’s it. No particle size, no other details, no datasheet published. This is not something that I would really trust my life with, compared to say 3M who publish extensive details on their tests and efficiency…

Industrial respirators / dust masks – 0.6 micron variable efficency


Generally these are classed by their protection rating. They are made out of harder fibres, and being hard, allow a tighter seal around the face and should also have a spring metal clip to form a seal around the bridge of your nose. There are 3 ratings:

  • FFP1 – Must filter out 80% of 0.6 micron particles that pass through the filter, and allows 25% of leakage – ingress of unfiltered air.
  • FFP2 – Must filter out 94% of 0.6 micron particles. The rest is the same as FFP1
  • FFP3 – Must filter out 99% of 0.6 micron particles. the rest is the same as FFP1.

FFP filters may or may not have an out vent. If they don’t, then there is a risk, given their rigidity and higher filtration capacity, that when you exhale, they “blow off” your face, and they don’t work well if you have a beard as there is not a large sealing area where the mask meets the skin on your face..

N, P and R class filters – Filters most particles down to 0.3 microns


As of writing this article, there are a lot of ads and claims around N95 filters, but there are several others around. N class filters are for normal particulate and vapor environments, and R and P class filters are specifically designed for organic (petroleum) vapors that the N filters will not filter as efficiently. R are rated for up to 8 hours normal continuous use and P are rated for up to 40 hours.

The number that follows defines the filtration efficiency – 85, 95 or 100 (sometimes called 99.9) percent.

Reusable filters

Full face

Here is where the rabbit hole gets a lot deeper. Re-usable is a relative term. The mask system is re-usable, but the filters are disposable.

The mask system may or may not have a full face giving eye protection, and the actual mask system allows a more positive fit around the face, even if you do have a beard. These masks are designed to fit a wide range of filter types, that can filter out almost anything, from fine dust to actual gas along with vapours of very specific and very nasty vapours, with a higher filtration efficiency than disposable masks.

The particulate efficiency is between 95 and 100% of 0.3 micron particles, and will work filtering specific vapors in the parts per million range, all depending on the filtration element installed.

Filter types – one size does not fit all!

Compared to plain particle filters, the number of different cartridges for full-face or half-face masks is huge and you must really select the correct cartridge for the correct application – select the wrong filter, and you may not be more protected than if you put a paper tissue over your nose… Most filters include a FFP2/3 or N95-N100 equivalent filter element but check the specs, cartridge filters come in many shapes, sizes and characteristics!

A WW2 gas mask may only work at filtering out some smoke and some basic chemicals, possibly no better than a cheap pollution mask, but others are designed to work in an environment polluted with radioactive heavy metals. You pays your money, yous takes your choice.


  • AX: Low-boiling point organic compounds (below 65°C)
  • A: High-boiling point organic compounds (above 65°C)
  • B – Inorganic gases
  • E: Acidic gasses
  • K: Ammonia
  • CO: Carbon Monoxide
  • Hg: Mercury
  • Reactor: Radioactive iodine
  • P: Particles (using the FFP1/2/3 number system)

These values can be chained together to identify a filter element that works for several categories, for example the unicorn filter, classified as A2B2E2K2-P3 that filters up to 0.3 microns, including some radioactive particles, acidic vapors, basic vapors, volatile organic vapors, more or less “everything” apart from carbon monoxide and dioxide.

unicorn filter
Powered by unicorns

Note that they will filter out your wallet too, as they start with a price point of about about 20 euros/dollars a pop, your mask may need two at a time, and at best, you will need to change them every 8 hours…

Is there anything better?

Yes and no. Filters have physical limits, N100 / FFP3 is about as good as it gets for filters, as for situations where the concentrations of airborne nastiness get too much for existing open-circuit filters, then then the next level is a closed-circuit Self Contained Breathing Apparatus, either with a compressed air cylinder or some sort of re-breathing system.

fire brigade

This does require a major air compressor (which also needs it’s own filter), and you need to drag the cylinder, taps, regulator, mask and harness. If you need this to work in a contaminated zone, then your air you are breathing is going to be cleaner and less polluted than the air that surrounds you. The air itself won’t be filtered much better than using a filter, but if you are working in a contaminated area that goes above and beyond what the characteristics of your filtering respirator, then this is the only way to be sure what you are breathing came from somewhere that was cleaner, but using this for coronavirus is a case of “just because you can does not make it a good idea”. Leave this to the emergency services!

International Standards between the US and the EU

The N, P and R standards are set by the United States National Institute of Occupational Safety and Health, along with the 85, 95 and 100 ratings

FFP1, 2 and 3 set by the European Union, under the EN149 standard.

These N85, N95 and N100 standards from the US correspond more or less to the FFP1, 2 and 3 standards in the EU, with the US standards filtering down to 0.3 microns, and the EU standards to 0.6 microns.

What are we trying to filter out anyway?

Coronavirus is mostly spread by contact or droplets of liquid containing the virus that are inhaled into the respiratory system. Most of these droplets are between 0.5 and 1 micron, so any filter that takes out droplets of this size will do the job, though the virus itself is about 0.12 microns, so evezn though there is not really any filter on the market that will protect against a random floating virus strand, they will stop most virus strands suspended in drops of liquid.


  • Surgical masks, uses and details on respirators: http://www.ansellhealthcare.com/pdf/ceu/respiratory_protection.pdf
  • Pollution filter masks: https://www.boulanger.com/ref/1128533?xtor=SEC-6903-GOO&xts=171153&origin=pla&kwd=&gclid=CjwKCAiAzJLzBRAZEiwAmZb0apgLE36_hwCkUjND_VVtHyRLaNKCUVjmfk3pn0y9bGhdr0_4npD6sBoCpAkQAvD_BwE&gclsrc=aw.ds
  • N, P and R respirators: https://www.majorsafety.com/blogs/news/whats-the-difference-between-an-n95-and-r95-respirator
  • Re-usable cartridge filters: https://www.3m.com/3M/en_US/company-us/all-3m-products/~/All-3M-Products/Safety/Personal-Protective-Equipment/Reusable-Respirators/?N=5002385+8709322+8711017+8720539+8720550+3294857497&rt=r3
  • Fitting a mask to ensure a good seal: More complicated than you would think: https://multimedia.3m.com/mws/media/811473O/3m-qualitative-fit-testing-poster.pdf?fn=Qualitative%20Fit%20Testing%20Guide%20Po
  • Gas mask filter category: https://en.wikipedia.org/wiki/Gas_mask#Filter_classification

One thought on “Do I need a respirator or facemask against Coronavirus?

  1. Andrew

    This is rather brilliant. I think I may have set you off down this path with my discussion about the virus… 🙂

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