After the World Health Organization (WHO) has advised against the use of masks with valves as a barrier against the coronavirus, both among health professionals and the general population, doubts have been raised about which masks are most effective in protecting themselves in the pandemic.
WITHOUT VALVE
In a new guideline with recommendations, WHO emphasized that the use of facial covers with removable valves or filters, mainly used by construction workers, is ‘inefficient’ or ‘useless’ to stop the spread of the virus, as the user can breathe out air that has not been 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, but it just beats the target, “explains the emergency director. of WHO, Michael Ryan, quoted in a bulletin of the organization.
The US Centers for Disease Control and Prevention (CDC) agreed, warning back in August that “holes in the material could allow respiratory droplets to escape and reach other people.”
A study by the US National Institute of Standards and Technology last November also found the shortcomings of this model of facial coverage to stop the coronavirus
By analyzing high-speed videos, engineer and researcher Matthew Staymates proved the behavior of airflow through masks with or without exhalation valves.
These valves make masks easier to breathe and more comfortable, but they are “suitable only if they are intended to protect the user,” such as hospital workers from infected patients.
However, the WHO has emphasized that health workers should use medical masks and without valves, given the results of these studies.
MEDICAL AND NON-MEDICAL: WHO USES WHICH?
In this sense, WHO continues to recommend to all health professionals to use medical masks (the usual masks in operating rooms, for example) in areas with a lower risk of airborne contamination (from aerosols) and those with more protection (N95, FFP2, FFP3) in areas of higher risk, such as areas of care for patients with covid-19.
Also for risk groups such as the elderly and people with chronic lung diseases, cancer, diabetes or cardiovascular problems, such mouth coverings are advisable, in contexts where a physical distance of at least one meter or adequate ventilation cannot be guaranteed.
The WHO recommends the use of medical masks at all times by health care providers and others sharing space with suspected or confirmed COVID-19 patients. This type of medical equipment is limited to these groups to avoid the shortage and encourage fair use.
For the general public, in areas where the coronavirus is transmitted by the community, the WHO recommends the use of non-medical masks (including cloth masks) in indoor areas such as shops, offices or schools, if a physical distance of at least is not possible are guaranteed. less a meter between people or good ventilation.
Apart from the type, the organization has insisted that the use of face masks should be mandatory and especially combined with other measures: hand hygiene, physical distance of at least one meter, avoid touching your face, cover yourself when coughing or sneezing, ventilate indoor areas and conduct contact tracing, quarantines and isolations.
“A mask alone, even when used correctly, is insufficient to provide adequate protection or source control,” adds WHO in its most recent guide.
FABRIC YES, BUT THREE LAYERS
When it comes to cloth masks, WHO has made it clear that the truly effective masks are those made with three layers: an interior that allows moisture to pass through, a filtering interlayer and a waterproof exterior.
However, the scientific director of the Brazilian Association of Infectious Diseases, José David Urbaez Brito, pointed out that this type of mask “has a useful life of three to four hours, as respiratory secretions moisten these tissues, especially cotton. And a moist substance loses its substance. identity as a barrier ”.
In this sense, 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, while providing eye protection, “should not be regarded as equivalent to masks with regard to protection against respiratory drops.”
SHOULD CHILDREN USE A MASK?
The WHO reiterated that children under the age of 5 should not wear masks and that children between 6 and 11 should use them, depending on factors such as the transmission of the virus through the community and the social and cultural environment.
In children over 12 years old, the same recommendations will be applied as in adults, according to the suggestions of the organization.
These suggestions should be weighed in clinical cases of immunosuppressed children, with serious underlying illnesses such as cancer, or people with mobility impairments, disabilities or special needs.
SPORTS AND FACE PROTECTION
Finally, the WHO warned that people should not wear masks during ‘vigorous intensity’ physical activities because ‘they may impair the ability to breathe comfortably’.
Instead, he recommended maintaining a physical distance of at least three feet from other people and ensuring good ventilation during exercise as “the most important preventive measure.”
“If the activity takes place indoors, adequate ventilation must be provided at all times by natural ventilation or a well-functioning or maintained ventilation system.”