Much as the intent of this article is laudable in its intent, it is misleading as to the relative merits of the various masks and perhaps misunderstands the mechanisms by which they can be used to inhibit aerosol transmission. It is therefore unnecessarily critical of the policy of hospitals to hand out surgical masks to visitors to replace their own.
Moreover, it takes no consideration of evidence from the Far East, where they have far greater experience of controlling infectious diseases and their death rates by Jan 2020 were 4000 times less than Western World averages, not the least due to the rapid distribution and take up of surgical masks.
The Type I & IIR surgical masks issued are not made of "paper". They are made of proven very fine filtration media. Several UK produced surgical masks have been certified to be 99.95% effective at capturing bacteria and solids, the standard test procedure. i.e. they only let 0.05% penetrate, 20 times less than the standard for FFP3 that only specifies 98%.
However, there are reasons to believe that surgical media may be even better at capturing the finest aerosols that carry the SARS-Cov2 virus, as their structure promotes coalescing into larger droplets and retention within the mask. Their breathing resistance is lower, such that leakage is less of a problem than some would suggest. They were deployed immediately by Taiwan and Vietnam without waiting for the "epidemiological evidence" sought by the West. They promoted their use everywhere there might be transmission, including in the home and on the youngest, a more sensible approach to infection control and the balance of risk. As a result, by Jan 2021 their deaths were only 10 and 27 respectively.
Their immediate decision to do so was critical to controlling infection and doing so should be equally effective in UK hospitals. Despite the potential for leakage around the mask, if both infected and susceptible are wearing them, the chance that they will receive sufficient dosage to become infected is radically reduced.
As the boy who stuck his finger in the dyke knew, the best place to control leakage is at source, so from the outset it has been obvious that, if those potentially infected could be persuaded to wear a mask approaching 100% effective in all high risk areas, we would need nothing else to control infection but performance is critical. Tests by Hong Kong Consumer Council confirmed that even the Type 1 surgical masks deployed in the Far East in early 2020 performed above specification at around 98%.
In contrast, homemade "Face Coverings" are far less effective. Even the new BSI standard only specifies 70% efficiency i.e. 30% can escape. Dosage transmission could therefore be of the order of 900 times higher, perhaps partially explaining why they proved so ineffective at controlling transmission and should have long since been outlawed.
As Engineers, back in April 2020, we immediately offered to develop a mask specifically to stop aerosols, as well as droplets and to prevent surface contamination with far less leakage, a simple development at miniscule fraction of the time/cost of vaccine development. 2 years on it is still needed for this and future pandemics. None of the existing masks is optimal for the task.
Had Professional Engineer Practitioners been represented on COBR, alongside SAGE Scientists and Academics, as has previously been the norm, far more solutions might have been deployed far faster and more coherent and informed advice offered in time to save lives.
Peter Hebard BSc, CEng, FIMechE, MCIWEM Chair of Engineers' Covid Task Force
Competing interests: No competing interests