Our anti-CODID-19 P3 (FFP3) filters, with European certification, only have a penetration rate of 0.5%, i.e. filtration at 99.95% (see diagram below). In comparison, FFP2 has a penetration rate of 6%. The FFP2 masks are made with plastic fibers (polypropylene), the P3 filters are made with glass fiber.

For information :

The average concentration of bacteria in hospital air is 350 to 700 CFU / m3 (colony forming units). In that of a patient room, this can reach 5000 to 7000 CFU / m3 when changing bedding. A single sneeze can generate up to 1 million droplets less than 0.1 µm (micrometer) in diameter, and as many as 150,000 droplet nuclei carrying bacteria have been counted.

A recent study published in the American journal of infectiology of 2006, concludes that the protection of N95 type masks does not necessarily provide adequate protection against viruses, given their size less than 0.3 µm, size of the NaCl particles. used during the certification made by the NIOSH (National Institute for Occupational Safety and Health).

In the United States, an N95 mask is certified to stop at least 95% of neutral NaCl particles with a diameter of 0.3 µm used as a standard aerosol. A P95 mask also has a particle efficiency of at least 95% and is resistant to oils, which is necessary in certain industrial environments. An N99 mask will filter 99% (like FFP3). The N95 and N99 masks are therefore also effective against the coronavirus.

(Source : Société Française des Infirmier(e)s Anesthésistes - French Society of Nurses Anesthesiologists)

covid-19, filter P3

In respiratory protection, the filter media (materials) used are made of fibres. The sieving effect is not responsible for trapping aerosols by a fibrous support. Several mechanisms intervene: Brownian diffusion, direct interception, inertial impaction and electrostatic forces.

Brownian diffusion

Small airborne particles have a disordered and random trajectory (Brownian agitation). Under the effect of this Brownian agitation, they can come into contact with a fibre of the filter and adhere to it (existence at the point of contact particle / fibre of an intermolecular force of attraction called Van der Waals force).

This mechanism is preponderant in the trapping of particles less than 0.1 µm in diameter. Its influence increases as the particle diameter decreases.

Direct interception

When a particle approaches a fibre at a distance less than the radius of the particle, it is intercepted by the fibre and adheres to it under Van der Waals forces. This mechanism applies to particles larger than 0.1 µm in diameter.


Inertial impact

Due to their inertia, the largest particles may not follow a current line passing around a fiber and collide with this fiber. This mechanism is predominant for particles with a diameter greater than 1 µm. Its influence increases with the size of the particle.


Electrostatic forces

Depending on the state of charge of the particle and the fiber, there are then several types of electrostatic forces which will deflect the particle from its trajectory and attract it towards the fiber where it will adhere.

(source : INRS National Research and Security Institute)

Other sources::

Filtering respiratory protection devices (FR)
Nanomaterials: a major issue for health and safety occupational health and safety. (FR)
Respiratory protection devices (FR)