Even before the official date of the presence of COVID-19 cases of extensive contagion in China, the writer had dealt - and is still doing - with disseminating information regarding the protection of the respiratory tract from the transmission of the new coronavirus. In the last month, much more has been written, said and disseminated on the subject by more or less authoritative sources about PPE and masks.

Unfortunately, also due to some inaccuracies contained in the information sometimes released, it is still not clear to many when one or the other garrison should be worn, what are their limits of use and other indications that, if misapplied, can significantly affect the effectiveness of the devices.

It must be said clearly that the topic is complex, not all questions find simple answers and, above all, there are nuances and facets that must be assessed on a case-by-case basis, just as there are still open questions against which we do not have certain answers. .

This premise is essential to allow the reader to interpret the present contribution with the right critical approach, which has no pretense of exhaustiveness, given the extension of the topic, but only of correctness with respect to the contents. So that the reader can research, also elsewhere, to deepen the topics covered, inviting him to always and only rely on authoritative sources (mainly scientific studies and updated information from institutional or recognized scientific reputation sites).

Brief description of the devices: surgical and filtering face masks

The first distinction to be made is between the so-called "surgical masks" and the "filtering ones". Much has already been said about the difference between the two and, presumably, this information is now known to most, and easily available, so we will treat it only in its essential lines.

The "surgical masks" are "devices for medical use", produced in compliance with the EN 14683 standard and have the essential function of protecting the patient from contamination that can come from vociferation and, in general, from the emission of saliva drops emitted by the operator wearing them. The material of which they are made is, in all respects, a filter for the penetration of microorganisms, but the absence of a specific ability to adhere to the face does not prevent the contaminant from reaching the respiratory tract of the bearer through the free spaces left between the edge of the mask and the face.

The "filtering face pieces" (although those to which we commonly refer are "half face masks") are produced in compliance with the EN 149 standard and belong to the category of "Personal Protective Equipment" (NB: there are also masks with interchangeable filter, produced according to the technical standard EN 143), they are almost entirely made up of a filtering material and may or may not have an exhalation valve.

Their function is to protect the wearer's respiratory tract from external agents: solid or liquid aerosols and are divided into three classes, in order of increasing protection: FFP1, FFP2 and FFP3. They do not protect against gases and vapors and, for the purpose of protection from microorganisms, only the half-masks FFP2 and FFP3 (or filters P2 and P3) can be considered suitable.

It is worth mentioning the existence on the market of devices certified at the same time as EN 14683 and EN 149: these offer security of protection for both the wearer and the patient but, especially in this situation, they are even more difficult to find.

Beyond the technical specifications of one or the other garrison, which, where necessary, we will give an account in the following, very prosaically what is relevant today to know is when it is necessary to employ one or the other. And it is here that the case series is so extensive that it has to resort to generalizations, with the risk of simplifying the question extremely.

Emergency measures: surgical masks such as PPE for the respiratory tract

A very important clarification must be made : for the entire duration of the emergency, the provisions contained to be equated with PPE for the respiratory tract, in place of which they can be used in the workplace.

This decision, while certainly extreme and emergency, is an obvious consequence of the lack of availability of filtering half masks on the market. And it has its foundations in a series of scientific studies [1] in which the absence of a significant difference in terms of exposure to the influenza virus among health workers who wear a class N95 mask [2] or a surgical mask [3] .

The comparison between surgical masks and PPE manufacturer for the respiratory tract is not the only "forcing" to which we are forced to face the epidemic, since even the same production and marketing of both devices has undergone a temporary derogation. Due to the fact that it is a medical device or a PPE, a manufacturer or an importer can now place them on the market behind the self-certification of their suitability and sending the documentation that can certify it to the Institute Superior.

Obligation to use PPE in the workplace

This said and, for the sole purpose of protection from infection by the SARS-COV-2 virus, since the measure of the social distance of 1 m is primary, in the workplace the obligation to wear the residual PPE only in cases where this minimum distance cannot objectively be maintained. Being PPE - whether they are masks or filtering face pieces - their function is and remains that of preventing residual risks that persist only after other collective protection measures (social distancing) are not feasible or sufficient.

The wearer protection offered by surgical masks and the FFP2 and FFP3 masks

As mentioned above, surgical masks do not have a specific protection requirement for the wearer, but the material of which they are made offers a filtration efficiency of at least 95% at the penetration of bacteria. As already said, however, this only concerns the filter and nothing can be said about operational efficiency. And the previous value, although high, is not absolutely significant of the real protection offered. However, it is worth mentioning some studies in the laboratory that show overall "real" protection that reaches even 90% (in others it reaches, at a minimum, 80%) and which also explain some performances that we will give account of shortly.

On the contrary, at least as far as the wearer is concerned, by definition, an FFP2 mask must have a total internal leakage loss of not more than 8% and FFP3 not more than 2%. These values, however, are guaranteed only if the respirator is correctly worn, does not wear a mustache, beard, sideburns and is kept on the face for the duration of the exposure, constantly and in the correct position. These are more complex conditions than it seems, so much so that Legislative Decree no. 81/2008 provides practical training for the use, including wearing, of these devices.

Some "experts", these days, have said that the filtering face pieces are not suitable for retaining the virus, since this, given its size - in the order of tens of nanometers - would pass through the meshes of the filter. This claim ignores the real mechanisms of operation of these devices [4] which, on the contrary, has been tested in the laboratory to be effective even with particles with a diameter of 0.007 microns, much smaller than a virus (even surgical masks have shown good filtration capacity with particles of this size).

In general, to put your heart in peace, just look at how these devices are currently used all over the world with the aim of protecting the wearer from coronavirus infection.

However, it is essential to remember that, even with reference to the FFP2 and FFP3 filtering facepieces, the risk can never be considered zero since, even if used in order to maximize their performance, these devices intrinsically admit a certain loss of seal towards the inside. .

Protection for those around us

The discourse changes when, on the contrary, the goal is to protect others from the risk of infection. In these cases, the appropriate device, as expressly designed and certified for this purpose, are surgical masks.

The FFP2 and FFP3 facials do not have an express requirement in this sense, unless there is a double certification, and this is even more true for those devices that have an exhalation valve that has the function of allowing the exhalation of exhalation without filtration, in order to reduce the expiratory resistance for the wearer and make it easy to wear for long periods, as well as prolonging the duration of the PPE.

This is a problem of no small importance but less impactful than one might think in the first instance, although it is important that everyone analyzes their own individual situation very well.

Some examples

It must be assumed that if two or more workers cannot maintain the safety distance of 1 m from each other, all of them, without exception, must wear personal protective equipment. In this circumstance, therefore, if everyone wore only surgical masks, these would prevent an eventual infection from spreading the infection.

Conversely, if everyone wore only FFP2 or FFP3, even if an infected droplet was emitted from the exhalation valve of one of them or from the same PPE (it is worth pointing out that at present there are no studies that confirm or deny this hypothesis), the other colleagues could not be infected as each bearer of a PPE. Obviously, for the reader the most relevant case is that in which some wear surgical masks and other PPE.

Mask wearers would thus potentially be more exposed to infection. However, it is the same equalization between PPE and surgical masks and, above all, the underlying studies, which affirm their good protection capacity in the "real world" which guarantees about the acceptability of the risk. It should also be considered that during the studies conducted, while the health worker wore a mask, the patient did not wear any "screen" that prevented the droplet from leaking [5] , in this case all workers wear a "barrier" that at least , if it does not cancel, it certainly reduces the emission.

What happens if some workers do not wear PPE or surgical masks?

And how to behave in those cases where some workers do not wear PPE or surgical masks? This situation simply cannot be contemplated, since where social distancing cannot be guaranteed, individual protection must be guaranteed. Alternatively and without exception, the activity cannot be performed.

Health workers and rescuers and use of PPE and masks

Additional situations that may arise are those related to health professionals or rescuers in general who must take care of potentially infected subjects. The operator must follow the instructions contained in the document attached to the Circular of 17 March 2020 of the Ministry of Health in which the use of PPE (FFP2 or FFP3) is available only in the case of activities.

Thus, the mask also ensures that the patient is healthy from the risk of infection by a potentially infected operator. However, many have wondered if there is a risk for the healthy patient if the healthcare professional wears a mask with an exhalation valve (for example, in the case of performing gold / nasopharyngeal swabs). Given that the question should also be asked in the case of FFP2 or FFP3 devices without a valve, since not even these are certified in accordance with EN 14683, in these cases the operator, in doubt, could wear a surgical mask over the half-mask filtering.

And for whom is it not a worker? PPE and masks ... And ordinary citizens

For ordinary citizens it should be remembered that the Ministry of Health, in accordance with the indications of the World Health Organization, provides that the masks must be worn only:

  • if you are infected;
  • if an infected person is to be seen at close range.

These indications are aligned with scientific evidence and also have the function of rationalizing the availability of masks on the market.

But we must also add more.

PPE and masks: instructions for use

Although the use of PPE and masks is apparently simple and intuitive, this is not the case. Not surprisingly, it is worth reiterating it,

The risk is that of wearing them badly: we have all seen, on television or on the street, people and even representatives of the institutions who wore the mask over their mouth, leaving their nose uncovered, frustrating the protection offered.

But there is also the risk of being contaminated by contact, touching them and then, for example, rubbing your eyes or, even, of using them for indefinite times, mainly because of their unavailability.

Furthermore, as anyone who went to the supermarket for shopping in these days will have verified, mask wearers have a tendency to think that they are unable to transmit the infection, thereby not respecting the social distance. They also tend to lower the level of attention with the risk of infecting themselves with risky behavior.

These and other reasons - extremely underestimated - must induce the citizen to remember that the first, fundamental and main forms of protection for him and others are:

  • social distancing;
  • Hand washing.

Given that there is an obligation to observe both of these measures; individual protection must be understood as a further prevention measure, but not strictly necessary in the current state of scientific evidence.

Having said this and without contradicting what has just been expressed, the use of masks can become a formidable form of contrasting diffusion when they are available to everyone. But here it is also worth talking about a controversial topic.

The standard refers to the production of these masks "in derogation from the current rules on the placing on the market" which obviously does not concern the individual citizen who decides to put a scarf on his face;

There are no rules that prevent - and therefore there is no need for authorization to do so - the individual citizen to go around dressed as a "cheerful surgeon" with a mask made with parchment paper. The rule in question does not concern him.

The purpose of the standard is to allow the large-scale production of these "devices" and their distribution on the market, without these "masks" being configured as PPE or surgical masks. So what would be their use?

In theory none. In practice, this is not quite the case, on the contrary.

Homemade masks or screens in the shape of a mask: do they have their usefulness?

Looking closely at the social phenomenon, we see that a considerable number of people have started to build “masks” of various materials in their homes. Those who did not, often went around with the collar of the shirt in front of the nose and mouth or with a scarf around the face. Their purpose was obviously to protect themselves. It was simply the wrong purpose.

A  scientific study [6] analyzed various materials, comparing them with a surgical mask and also carrying out various tests with carriers, demonstrating a low protection capacity of the wearer of homemade masks, but a certain effectiveness of these in preventing the spread of droplet.

Therefore, without prejudice in any case to compliance with the rules of hygiene and social distancing, these "mask-shaped screens" which could be distributed and / or placed on the market, can be useful in further reducing the risk of contagion.

Attention: in no case can these vehicles be used in the workplace where the use of an individual protection device is necessary.