Consultant Orthopaedic and Trauma Surgeon and Visiting Professor
Royal London and Barts and The London Children’s Hospitals,
Barts Health NHS Trust, London, England
Let’s start with the most basic face coverings, the homemade non-manufactured face masks that are easy to put together e.g. using scarves, bandannas or handkerchiefs. To be honest, the level of protection here is negligible. Although it is probably better than nothing, clearly we would not wear these in a healthcare environment! In terms of droplet and aerosol transmission (which can contain coronavirus), the level of protection is minimal for the smallest droplets, although increasing the number of layers may be more effective. So when you are out and about in public, these face coverings are better than having nothing on but do be aware of their limitations.
The next level of protection is from manufactured non-medical grade face masks (including homemade sewn converings). Again, to be clear, the level of protection against droplets and aerosols is minimal and although they are used by the public frequently, remember again that social distancing, hand hygiene and avoiding touching the mask or face is much more important
Type I (Level 1): provide low barrier protection for use for low-risk, nonsurgical procedures and interactions at the frontline of healthcare where the wearer is not at any risk of fluid or droplet exposure. An ear loop mask that is readily available for purchase is considered a level 1 mask. These level 1 masks can be used when you are in contact with mild or asymptomatic suspected or confirmed cases of COVID-19 and if this is all that is available, consider using an additional full-face shield. Bacterial efficiency is in the region of 95% or greater. Type 1 masks are available in washable, breathable and reusable versions. In the UK, these masks should comply with the EN14683:2019 Type I standard.
Type II & IIR: provide moderate barrier protection where there are low-to-moderate levels of aerosols, sprays and fluids. An example of frontline healthcare use is when minimal exposure to droplets is likely to occur e.g. in emergency departments for wound dressings. Bacterial efficiency is in the region of 98% or greater. Type II are made up of a 3 ply construction while type IIR are slightly thicker with a fluid repellent layer. Note that the fluid resistant properties of Type IIR masks are specifically for close proximity environments such as care homes and hospitals and will protect against fluid transfer from coughs and sneezes. The World Health Organisation certifies Type IIR (and FFP2 masks) for use in close clinical environments e.g. in healthcare settings with known COVID-19 patients. In the UK, these masks should conform to the EN14683:2019 Type IIR standard.
N95 (FFP2) respirators were designed to be used in healthcare settings where respiratory protective equipment is needed from high-risk particle generators such as aerosol generation in patients with highly infectious diseases (such as tuberculosis) and smoke generation from procedures (such as electrosurgical dissectors) and therefore, standard surgical masks should not be used.
Particulate filter respirators, in comparison to the other types of masks available, offer a much closer fit to the face but this can become uncomfortable over prolonged periods of wear. In high-risk healthcare settings, fit testing is essential to ensure that leakage is minimal during respiration.
N95 respirators are held in place by elastic ear loops or head straps and provide excellent protection. However, they cannot be shaped any further to your face for closer fitting and there is a maximum of 8% leakage to the inside.
Following on N99 (FFP3) respirators, on the other hand, are better shaped to your face for a tighter fit (and so can be slightly more uncomfortable) and the additional valve does help make breathing easier.
N99 respirators only have a maximum leakage of 2% to the inside and the valve also reduces moisture buildup, allowing the mask to be worn for a longer period of time.
In general, N95 respirators give the most protection needed in high-risk healthcare settings, although we as surgeons do avoid the use of valves in operative cases as although the one-way valve filters the inhaled air, exhaled air is expelled out through the valve.