Securing supplies:
Closing supply chains.

Good filters work like doormen: They only let through what is wanted. This task becomes all the more complex, the smaller the particle size is which needs to be filtered. A simple sieve effect, as known from sandboxes, is no longer effective to handle very small particles, such as viruses and bacteria. In the case of face masks, for example, an additional combination of effects such as inertial impaction, diffusion, and electrostatic attraction are active at the same time.

• High filtrationefficiency: As many particles as possible are entrapped in the filter.
• Low pressure drop: It is easy to breathe through the filter.
• High absorption capacity: As many particles as possible can be absorbed before the filter becomes clogged and pressure drop increases. Moisture in the breath reduces filter capacity. This is why filters must be replaced at regular intervals.
• Low cost: Filters are often the functional layer of a disposable product, as is the case with medical applications.

• Meltblown nonwovens consist of extremely fine fibers that are on average 1 µm thick and of endless length. By comparison, a cotton fiber is 12-35 µm thick and 15-56 mm long
• Meltblown nonwovens are produced in different thicknesses and densities. Example: A 25 g/m meltblown nonwoven consists of max. 500 fiber layers.
• Due to its structure and its additional electrostatic charge, all the filter effects act simultaneously in a meltblown nonwoven. Even the minutest particles, which may contain the coronavirus, are entrapped reliably.
• Filters made from meltblown combine high performance with good wearing comfort (easy to breathe) since a proper balance between filtration efficiency,  absorbtionstorage capacity, and pressure drop can be realized. Moisture in the breath reduces filter capacity. This is why  filters must be replaced at regular intervals.
• The material is low-cost and can be produced rapidly in large quantities.

There are many different medical face masks. They are basically divided into two main categories with distinct differences in structure. What all masks have in common: the filter layer made of meltblown which is designed with different layers and basis weights, depending on their application:

Face masks
Standard EN 14683, Types I, II, IIR

Face masks, also known as surgical masks, primarily protect the wearer from the environment.

Respirator masks
Standard EN 149 FFP 1-3

Respirator masks protect the wearer from infection. These masks are required by staff that come into contact with people who are already infected. It also offers protection in the opposite direction, provided the respirator mask is not fitted with an exhalation valve.

Foldable respirator:

All medical face masks are equipped with so called N95* and N99* meltblown nonwovens, whether they are face masks or respirator masks. Nevertheless, the nonwovens differ considerably from one another since the specifications are always linked to the size of the particles filtered. An N95 meltblown to filter building dust requires a different production process than an N95 meltblown to filter viruses.

Therefore, when ordering meltblown material, the filter performance required must be specified exactly as well as the intended purpose of the filter. It is not enough to specify simply N95 nonwoven or N99 nonwoven.

* The values N95 and N99 indicate the percentage of a specified particle size range absorbed by the material.

Spunbonded nonwovens provide:

• Strength
• Hydrophobia (rejection of water and blood)

Meltblown provides:

• Barrier and filter function against bacteria and viruses
• Untreated SMS nonwovens are not suitable for use in the operating room.

Protective clothing that is worn in the operating room must be alcohol-repellent. This property can only be achieved by post-treatment. For this purpose, the nonwoven fabric is subsequently treated with fluorocarbon in an immersion bath and dried again in a heating oven.

Without a post-treatment of SMS nonwovens, the protection against water and blood is destroyed as soon as the material comes into contact with alcohol.