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The LCC Guide to Masks

It looks like we will all be getting more and more familiar with masks over the next few months.  Having done our mask homework we’d like to share what we learned with as many people as possible – so if you are reading this, please pass it on to anyone that you think might be interested or in need of a little prompting! Many of you will be far better informed about PPE than we are but we are hoping that this whistle-stop tour of masks will give the rest of us a place to start.

The general purpose of a mask is to provide a barrier between the room air and the relatively unguarded damp pink linings of our mouth, nose and throat, collectively called the mucous membranes. If we want this barrier to be 100% effective, then a plastic bag over the head would do the job nicely but this clearly poses problems. We need to be able to move air through the barrier, and so an effective and practical barrier needs to be able to filter the air to some degree as it moves through from one side to the other, a bit like the UK Border Force permits travel but filters out contraband and undesirables at air and sea ports.

So what are we trying to block? Today, 2020, it is coronavirus particles. These particles are, needless to say, tiny – 120nm – which is about 0.00012mm. It turns out that they form clumps of less than 5µm (0.005mm) which can stay suspended in the air indefinitely, or greater than 5µm which will slowly fall to the floor but can be projected up to 6 metres by coughing or sneezing. Think of this as minute airborne particles that may or may not fall to the floor and that we can unwittingly breath in or out, in addition to the larger – and visible – sort of virus-laden droplets that make your tissue damp when you sneeze into it. Watching an ex-smoker Vaping gives us a graphic illustration of how far someone’s breath plume normally extends – that vapour cloud you see and the associated smell that hangs in the air is their last out-breath. I have included below a link to a journal article from the Lancet for further reading, but this won’t be in the test!

So how do we choose the right sort of barrier to wear? By thinking about what we want the barrier to achieve, and then how effective we need it to be.

Firstly, do you want to protect yourself or someone else? If you are working with dust, asbestos or known COVID sufferers, then you need a barrier that stops airborne particles from getting in. These are called RESPIRATORS and we see them being worn by troops and police on the News, in your house when the builder starts to pull down the kitchen ceiling, and most recently in hospital COVID intensive care units. RESPIRATORS ONLY PROTECT THE WEARER because their effectiveness is tested in the direction of the In-Breath. They offer no protection to people around you because the outgoing breath is not filtered – or at least not tested or certified as such – although it may be better than nothing.

Alternatively, if you are working around someone vulnerable to infection or with an open wound, then you need the barrier to stop airborne particles moving from us and onto that vulnerable person. This is what a SURGICAL MASK does. Wearing a surgical mask is like catching a sneeze in a tissue, but as well as flying mucous it will catch the virus clumps that we might breath out. In Europe we never really saw surgical masks outside of Holby City until this year, but they have been widely used in public spaces in the far east and south-east Asia for a while, with the aim of reducing the spread of coughs and colds. SURGICAL MASKS ONLY PROTECT OTHER PEOPLE AND NOT THE WEARER because they are only tested in the direction of the Out-Breath. They may however give you better-than-nothing protection.

Both Respirators and Masks have a rating standards system to let you know how effective they are. The UK, USA and China give their Standards different names, but in general they filter to either a 95% or a 98-99% level.

Respirators in the UK are referred to as Filtered Face Protection (FFP) and the ratings are called FFP2 or FFP3, filtering 95% or 99% of particles respectively – but only on the in-breath, remember. FFP can be stitched and folding, or moulded, cloth or rubber, replaceable gas-mask style filters or not. The effectiveness is tied to the rating, and the design details are all about comfort and practicality. You may also see KN95 or N95, – these are US and Chinese standards equivalent to FFP2 (95%) filtration and N99, equivalent to FFP3 (99%) filtration.

Blue pleated disposable masks are becoming commonplace, but those readily available on the High Street are typically untested and not conforming to any particular standard. Genuine surgical masks are given the rating of Type1 “(T1)” or Type2 “(T2)”, which stop 95% and 98% of exhaled particles respectively. Remember however that neither T1 or T2 mask will prevent you from inhaling the sort of airborne virus clumps that we described earlier, but that isn’t their purpose. Surgical masks are there to protect the people around you. Both Types may have the rating of “(R)” added to them, and this means that there is an additional layer added to the mask which will stop inbound droplets that can be seen with the naked eye – but not the small clumps. Essentially, if someone sneezes in the wearer’s face, the (R) rated mask will stop the mucous but not the flying virus particles. Putting it together, you will see T1, T1(R), T2 and T2(R) masks on sale. If you are buying a blue mask, look for an EN14683 number or a Type on the box – if it doesn’t carry that mark then it is “Better than Nothing” at best. Not all masks are surgical!

Hand made and commercially available cloth masks are appearing from a multitude of sources, and the best current advice in the medical literature is that they are “effective” in limiting the spread of COVID19 – but only in low risk environments – because they reduce the number of large droplets that get from the wearer to the outside. There is clearly no Quality Assurance, testing or rating applied to cloth masks so we have no idea what percentage is being filtered, but when limited to the right context they are effective. What is the right context? When you are not getting into close contact with others – essentially when social distancing is generally possible, but you will inevitably pass close to others for brief periods of time. Shopping, school runs, that sort of activity. When are cloth masks not appropriate? When you are in a closed space or close contact with someone for more than a few minutes, or when you are with a vulnerable person. In summary, Cloth masks are somewhere between “Effective” and “Better than Nothing”, depending on the circumstances! Our experience is that our kids love the Spiderman Masks made by the loveliest patient in the world – you know who you are – and this probably makes the difference between them wearing a mask and not, and this feels like a good way to get them used to best-practice for the future.

What are we wearing in the clinic? In accordance with PHE guidance we are wearing T2(R) surgical masks to protect our patients, and we are issuing the same type of mask to everyone who comes into the building to protect us. Respirators and cloth masks don’t unfortunately offer us adequate protection in a healthcare setting, and not all blue surgical-looking masks are created equal. We really hope this brings some clarity to a complex topic that is new to most of us.