Vol.2_TTRI CNS14755 test report, is the particle size 0.26um or 0.075um?

You must have discovered the difference between [CMD] & [MMD].

What is the test particle size of CNS14755?

The answer is: The test particle size of CNS14755 is 0.075um [CMD], which is also 0.26um [MMD].
Yes! You must have discovered the difference between [CMD] & [MMD].

What exactly is CMD/MMD?

CMD = Count Median Diameter = Particle count median diameter.
MMD = Mass Median Diameter = Mass Median Diameter.

Simply put, it is very difficult to produce a large number of fine suspended particles in the air with a fixed particle size. There will definitely be an error in the particle size. Generally, it will show a Gaussian-like distribution, and then several standard deviation ranges will be used as the particle size according to the experimental requirements. allowable value. For example, the NIOSH test to which N95 belongs takes six standard deviations of the particle size distribution measured by the instrument. Within this range, everything will be included in the calculation of CMD or MMD.

The definition of CMD is " the total number of particles larger than the CMD particle size is equal to the total number of particles smaller than it ";
The definition of MMD is
" the total mass of particles larger than MMD is equal to the total mass of particles smaller than MMD ."

From the above definition, it can be clearly understood why CMD is usually much smaller than MMD. Because the number of small-sized particles accounts for a large amount of the total distribution, their mass accounts for a small amount. That’s why there is an incomprehensible phenomenon that 0.075um [CMD] is actually the same particle size as 0.26um [MMD].

By the way, the commonly referred to as PM2.5 refers to 2.5um [MMD]!

After understanding the above definition, next time you look at the filtration report provided by the manufacturer, remember to confirm the particle size unit before making a judgment~


*https://goo.gl/KWsFNt (CMD to MMD conversion method)
*https://goo.gl/o2I1Yg (CMD & MMD)

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