The humidity generated by the rain reduces the effectiveness of the mask, which filters less well and lets the virus pass through.
- The static electricity of the fibers of the fabric of the mask disappears with humidity and no longer stops the droplets of sputters.
- It should not be dried with a hair dryer: hot air completely destroys the sterility and therefore the usefulness of the mask.
- When it rains, you must have a spare mask and/or go out with an umbrella to protect it.
The extension of the obligation to wear a mask in many French cities as autumn slowly takes shape questions its effectiveness in the event of rain. On this subject, the answer is clear: if your mask is damp or wet, it loses its effectiveness. It is therefore necessary to change it for a dry one. It is therefore better, when it rains, to go out with a spare mask to continue to protect others and yourself.
Dry it with a hair dryer, a false good idea
Humidity changes the properties of the mask which no longer protects effectively when wet. “The degree of protection of the masks is measured by the static electricity of the fibers of the fabric which stops the droplets of the sputtersprecise the French Association for Standardization (Afnor). However, if the mask is wet, this static electricity disappears and the droplets pass more easily.” The mask no longer plays its role as a filter and only does figuration. “To simplify, the viruses are smaller than the holes in the mask but they are still caught, because when you breathe the viruses stick to the fibers of the mask.continues Isabella Annesi-Maesano, director of research at the National Institute of Health and Medical Research (Inserm), interviewed by Point. But if the material is wet, these fibers work less well and let the virus pass through: you have to put on a dry mask as soon as possible..”
These indications have led the Directorate General for Health (DGS) to recommend, in a press release published on July 30about the wet mask of “change it because its effectiveness is no longer guaranteed”. Before leaving home, it is better to anticipate and provide a spare mask or use an umbrella to avoid splashing water on it. And if that is not possible, drying your reusable mask, with a hair dryer for example, is a false good idea. “It is a sterile structure that is made to stop the virus, with hot air we totally destroy the sterility and therefore the usefulness of the mask”, specifies Béatrice Lognos, general practitioner in Saint Georges d’Orques, in France 3.
Reminder of the rules for the use of the mask
Besides avoiding wearing a wet mask, other precautions must be observed for it to be effective. “It must be washed whenever it is soiled, wet or incorrectly positioned on the facerecalls Afnor. It should not be put in a waiting position on the forehead or under the chin during and after use.” In addition, the mask, whether fabric or disposable, should not be worn for more than 4 hours. “During this period, the mask can only be used several times if it is removed according to the instructions, temporarily stored or hung up to offer the least possible contact, and put back according to the instructions.”, adds the Association.
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