After the World Health Organization (WHO) recommended against the use of valve masks as a barrier against coronavirus, both among health care workers and the general population, doubts arose as to which masks are the most effective for the pandemic is protected.
WITHOUT VALVE
In a new guide of recommendations, the WHO emphasized that the use of facial coatings that have removable valves or filters, used mainly by construction workers, is “inefficient” or “useless” in terms of containing the spread of the virus, as the user could exhale air that is not sufficiently filtered.
“The danger is that if you wear a mask with a valve and you are infected, you can expel infected aerosols. In other words, it defeats the purpose of wearing a mask. It is not dangerous for you, it just defeats the purpose,” the emergency director explained. of the WHO, Michael Ryan, quoted in a bulletin of the organization.
The US Centers for Disease Control and Prevention (CDC) agrees with this, warning since August that “holes in the material can allow respiratory drops to escape and reach others.”
An investigation by the US National Institute of Standards and Technology in November last year also found the shortcomings of this facial coating model to stop the coronavirus.
Analyzing high-speed videos, engineer and researcher Matthew Staymates highlighted the behavior of airflow through masks with or without exhalation valves.
These valves make masks easier and more comfortable to breathe, but are “only suitable when they are designed to protect the user,” such as hospital workers from infected patients.
However, the WHO insisted that health workers should wear medical masks without valves, given the results of these studies.
MEDICAL AND NON-MEDICAL: WHO USES WHICH?
In this direction, the WHO continues to recommend to all health personnel the use of medical masks (those common in operating rooms, for example) in areas with a lower risk of airborne infection (by aerosols) and in those with higher protection (N95, FFP2, FFP3) in higher risk areas, such as covid-19 patient care areas.
Mouthwashes of this type are also recommended for at-risk groups, such as the elderly and people with chronic lung disease, cancer, diabetes or cardiovascular problems, in contexts where a physical distance of at least one meter cannot be guaranteed. or adequate ventilation.
The WHO suggests the permanent use of medical masks by caregivers and others who share space with patients suspected or confirmed by COVID-19. This type of medical equipment was limited to these groups to avoid its lack and to encourage reasonable use.
For the general public, in areas of Community coronavirus transmission, the WHO recommends the use of non-medical masks (including cloth masks) in indoor spaces, such as shops, offices or schools, if a physical distance of at least cannot be guaranteed. less than a meter between those present or good ventilation.
Beyond this type, the organization insisted that the use of masks should be mandatory and, above all, combined with other measures: hand hygiene, physical distance of at least one meter, avoid touching the face, covering while coughing. or sneezing, ventilating indoor environments and tracking contacts, quarantines and insulation.
“Only a mask, even when used correctly, is insufficient to provide adequate protection or control of the source,” adds the WHO in the latest guide.
FABRIC YES, BUT WITH THREE LAYERS
With regard to fabric masks, the WHO stated that those that are truly effective are those that are made with three layers: an interior that allows the passage of moisture, a filter intermediate and a waterproof exterior.
However, the scientific director of the Society of Infectious Diseases of Brazil, José David Urbaez Brito, stressed that this type of mask “has a useful life of three to four hours, because respiratory secretions moisten these tissues, especially cotton. And a damp fabric loses its barrier identity.
In this regard, the WHO warned that industrially manufactured masks of this type “must meet the minimum thresholds related to the three essential parameters: filtration, breathability and fit”.
In its terms, the WHO also clarified that masks or visors, although providing eye protection, “should not be considered as the equivalent of masks in terms of protection against respiratory drops”.
WOULD THE CHILDREN USE A MASK?
The WHO reiterated that children under the age of 5 should not wear masks and that those between the ages of 6 and 11 should use them according to factors such as community-based transmission of the virus and the social and cultural environment.
The same recommendations will apply to children over the age of 12 as to adults, according to the organization’s suggestions.
These suggestions should be balanced in clinical cases of immunosuppressed children with serious underlying diseases, such as cancer, or those with a mobility problem, disability or special need.
SPORT AND FACIAL PROTECTION
Finally, the WHO warned that people should not wear masks during “vigorous intensity” physical activity, as “they can reduce the ability to breathe comfortably”.
Instead, he recommended keeping a physical distance of at least one meter from other people and ensuring good ventilation during the effort as “the most important preventive measure”.
“If the activity is to be carried out indoors, adequate ventilation must be provided at all times by natural ventilation or by a ventilation system which functions properly or is maintained.”