Disposable face masks
Find out how they are made and how they work
Surgical face masks are Class I Medical Devices. Their use reduces the risk of direct and/or cross-contamination from viruses and bacteria that can cause infections to operators and patients, and protects against chemicals used during medical procedures.
Understanding how the face masks are made and their function also means avoiding potentially dangerous errors such as reuse, disinfection or sterilization.
How are surgical masks made?
Surgical face masks have a multi-layer structure, resulting from the combination of different materials: the outermost and innermost layers are made of non-woven fabric (TNT), mainly polypropylene, which ensures better bacterial filtration and greater permeability and adherence. The outermost part is made water-repellent, so that any type of liquid is blocked on the outside. The innermost layer, in direct contact with the wearer’s face, is hydrophilic, i.e. it absorbs and retains sweat, humidity or small particles of saliva that would otherwise disperse into the surrounding air.
Between these two layers, one or more filters are placed, depending on the type of face mask, in compliance with the regulations: the particulate and antibacterial filter retains almost all particles and pathogens of a certain size, load and concentration, while the polymer filter ensures resistance to fluids.
The regulations in force
Surgical face masks are Medical Devices, and must comply with the European standard EN 14683, which requires, more specifically, a test of their resistance in accordance with ASTM F2100 standards.
ASTM International, one of the world’s leading standard development organisations, specifies the performance requirements for disposable masks according to five different criteria:
- Bacterial filtration efficiency (BFE) indicates the percentage corresponding to the bacterial load of more than 3 micron effectively filtered by the mask;
- Particulate filtration efficiency (PFE) indicates, in a similar way, the percentage of particles smaller than micron size that the mask is able to filter;
- Liquid penetration resistance defines the ability to retain on the outside any type of fluid that may come into contact with the mask as a result of splashes or spraying;
- Differential pressure (Delta P) establishes respiratory fatigue when using the mask and objectively measures its breathability;
- Flammability calculates, in time, the resistance of the device when exposed to open flame.
The result of these tests allows the face masks to be classified by level, in a range from I to III.
Masks are disposable devices, and must be replaced when exposed to atomised substances or liquids, and in any case after treating each patient.
Is it possible to reuse the disposable face masks?
No, the face masks cannot be reused. Reuse of the face masks carries the risk of self-inoculation, i.e. the risk of coming into contact with and/or transporting viruses and bacteria remaining on the internal and external surfaces, and the consequent possibility of contagion.
Is it possible to sterilize the disposable face masks in order to reuse them?
As regards sterilization, there is an important point to be made: the key question is not whether or not the bacterial contaminants can be eliminated from the face mask by treating it with chemical agents, steam, radiation or other methods, but the fact that such treatments damage the Medical Device, reducing its protective performance.
To be more specific, the stress to which the face mask is subjected during the sterilization process could affect its filtration efficiency, by altering the structure of the material that makes up the particulate and antibacterial filter.
In addition, there is no confirmation that pathogens are eradicated after the face mask has been treated, so there is a risk of wearing a contaminated – and at the same time ineffective – device that is dangerous both for the wearer and others.