Comparison of filtering performance of several masks
Recently, many people asked questions about masks, such as "can this mask work?" "how does this mask work?" "... With these questions, I tested the filtering efficiency of the five masks at hand. The following is my test process and test summary. I hope my test will be helpful to you in choosing masks.
Measuring instrument: 1. Hand held particle tester to measure particles: 2.5 μ m and 0.3 μ m count; 2. Professional hair dryer (including cold wind gear)
Measuring mask: from top to bottom in the picture, N95 mask (unsealed for 3 months, used n times), medical mask 1 (light blue, not used), medical mask 2 (blue, not used), ordinary dust mask 1 (black, used twice), ordinary dust mask 2 (blue, not used)
Measurement method:
Fix the hand-held particle tester on the desktop, face the air outlet of the electric hair dryer to the sampling port of the particle tester at a distance of about 20cm, turn on the cold air of the electric hair dryer and adjust it to low-grade air;
Turn on the particle tester to measure the particle concentration in the environment (closed room), that is, the particle concentration at the sampling port of the particle tester. The test time is 20 seconds. After the measurement, record the quantity of 0.3 micron and 2.5 micron particles respectively;
Completely cover the sampling port of the particle tester with N95 mask or other masks, measure the concentration of particles filtered by the mask filter material, and the test time is 20 seconds. After the measurement, record the quantity of particles of 0.3 μ m and 2.5 μ m respectively;
Repeat steps 2 and 3 for the remaining 4 masks.
The following pictures show each mask and the corresponding particle removal rates of 0.3 μ m and 2.5 μ m, which can be seen:
N95 mask (the top one) has the highest removal rate of 0.3 μ m and 2.5 μ m particles, both exceeding 90%;
The removal rates of 0.3 micron particles and 2.5 micron particles were 90% and 51%, 100% and 75%, respectively;
The performance of the two ordinary dust masks is poor. The removal rate of 0.3 micron particles by the three-layer black mask is only 20%, and that of 2.5 micron particles is only 60%; the removal rate of 0.3 micron particles by the two-layer blue mask is even 0 (invalid), and that of 2.5 micron particles is only 42%.
My suggestions for choosing masks:
Choose according to the environment. In general occasions, the crowd is not dense and the probability of infection is small. It is OK to choose a mask containing three layers of filter materials; for highly exposed people, N95 or regular medical masks with quality assurance should be selected. Of course, the higher the level, the stronger the protection ability;
Generally, for masks containing melt blown filter materials, the thicker the material, the better the quality and the higher the filtration efficiency;
Try not to choose masks with only two layers or even one layer of filter materials;
If there is no more choice, wearing a mask with two layers of filter material also has a certain protective effect on droplets.
It is hereby stated that the above test equipment is not a professional desktop equipment, and the test environment is not a formal test environment. However, the horizontal comparison of test data is of reference value, because a friend of mine also tested the second kind of mask, namely light blue three-layer mask, in a formal laboratory. His test result is that the removal rate of 0.3 micron particles is 85%, which is higher than that of It's very close to 90% I measured!