What do BFE and PFE Tester mean in mask testing?

What do BFE and PFE Tester mean in mask testing?
The filter material of mask is basically melt blown non-woven fabric of polypropylene material. The pore diameter and thickness of fiber affect the filtering effect. Particles with different diameters are filtered by different principles, such as particle volume, impact and diffusion, which are blocked by fibers, and some particles are filtered by electrostatic fibers through electrostatic attraction.

The test of filtration efficiency is carried out under the particle size specified in the standard. Different standards will use particles of different sizes for testing. Average particle diameter 3 is often used for BFE μ M bacterial aerosol particles, while PFE generally adopts sodium chloride with a diameter of 0.075 μ M particles. From the perspective of filtration effect, PFE has higher effect than BFE.

In the standard test of kn95 respirator, the aerodynamic diameter is 0.3 μ M is the test object, because particles larger or smaller than this diameter are easier to be intercepted by the filter fiber, while 0.3 μ M so that particles of intermediate size are more difficult to filter. Although the size of the virus is very small, it can not spread in the air alone.

Particle filtration efficiency (PFE): for the filtration effect of micro particles, the larger the value, the better the filtration effect.

Bacterial filtration efficiency (BFE): the greater the value, the better the filtration effect.

In yy0469-2011 medical surgical mask standard, it requires BFE not less than 95% (3) μ M), PFE not less than 30% (0.075 μ M particles). The function of surgical mask is to protect large particles, such as saliva, splashed blood, droplets and the bacteria or viruses contained in the general medical environment. This mask can also block the droplets exhaled by many wearers, reduce the probability of two-way infection, and require disinfection of the mask to prevent pollution of the medical environment. If you wear this mask, you can obviously feel that its ear strap tension is very small, the veneer effect around the mask is not good, and the respiratory resistance is relatively small. However, due to the low sealing with the face, most of the inspiratory air will leak from unsealed places when wearing, and its protection ability in the polluted environment with large concentration is not strong. Such masks usually require a liquid resistance test on the splashed synthetic blood to help reduce the ability of liquid splashes to contact the wearer. In China, this kind of mask does not belong to personal protective equipment, it belongs to medical equipment.

Gb2626-2006 standard for respiratory protective masks. Respiratory protective masks are personal protective equipment, and their main filtering requirements are for PFE. This kind of mask is usually three or more layers, which mainly depends on the middle melt blown layer for filtering. It is used in environments exposed to high concentration pollution or with high concentration particle risk. It is structurally Zui different from the surgical mask in that its sealing performance is much better. The veneer effect and the pulling force of wearing the elastic band of this mask are much stronger than that of the surgical mask. If you have used this mask, you will find that breathing is much more laborious than that of the surgical mask. This mask needs to have a certain structural support strength, which leads to large respiratory resistance because of its good sealing.

Surgical masks are different from respiratory protective masks in terms of functional focus. Surgical masks focus more on the protection of splashed droplets. Due to the poor sealing of surgical masks, when actually wearing them, the filtering effect of surgical masks on particles in high concentration environment is not as good as respiratory protective masks.

Of course, there is also gb19083-2010 standard for medical protective masks. This standard is equivalent to respiratory protective masks, which increases the requirements for blood protection, high temperature and sterilization. However, the PFE filtration efficiency level is differentiated according to the level. Zui the lower level also needs to meet the requirements of kn95 ≥ 95% filtration efficiency, level 2 ≥ 99% filtration efficiency and level 3 ≥ 99.97% filtration efficiency. The medical protective mask is mainly used for respiratory protection of occupational medical staff and belongs to medical equipment.

The PFE test of surgical mask is very different from that of respiratory protective mask, which can not be compared. Under the test conditions of gb2626-2006, the filtering efficiency of surgical mask with high PFE (> 95%) may be less than 70%, so this is also the reason why the filtering efficiency of kn95 mask made of surgical mask bfe99 filter material often does not meet the requirements.