{"id":1568,"date":"2024-10-04T09:56:55","date_gmt":"2024-10-04T02:56:55","guid":{"rendered":"https:\/\/filterfinevn.com\/?p=1568"},"modified":"2026-06-11T11:05:08","modified_gmt":"2026-06-11T04:05:08","slug":"5-nguyen-tac-co-ban-cua-may-dem-hat","status":"publish","type":"post","link":"https:\/\/filterfinevn.com\/en\/5-nguyen-tac-co-ban-cua-may-dem-hat\/","title":{"rendered":"5 FUNDAMENTALS OF PARTICLE COUNTERS"},"content":{"rendered":"

<\/p>\n

5 Fundamentals Of Particle Counters<\/strong><\/h1>\n

Particle counters do just that: they count particles. They are used in\u00a0cleanrooms<\/strong><\/a>\u00a0to count and size the particles in the air so the cleanroom can stay in proper working function and meet crucial certification criteria. The fundamentals of particle counters are relatively simple. You need to know how and why they work. If you have a basic grasp of these fundamentals, you\u2019ll be on your way to better understanding particle counters.<\/p>\n

1. Particle Sizing And Why It Matters<\/strong><\/span><\/pre>\n
Our\u00a0particle counters<\/strong><\/a>\u00a0detect some tiny particles. They are so small, the only way to detect them is through high-accuracy lasers, but we\u2019ll get to that in a minute.<\/p>\n
As an example, these are the sizes of some common particles:<\/p>\n
Average human hair: 100 microns<\/p>\n
Salt grain: 60 microns<\/p>\n
Pollen: 15 microns<\/p>\n
Bacteria: 5 microns<\/p>\n
Viruses: 0.1 microns<\/p>\n
COVID-19 virus: 0.06 to 0.14 microns<\/p>\n
ISO 14644-1<\/strong><\/a>:2015 identifies particles as smaller than 0.1 microns as ultrafine particles and particles larger than 5 microns as macro-particles.<\/p>\n
But advancing technologies, such as photography, are driving us to detect particles even smaller, such as those in the nanometer range. So we work every day on technology to detect these particles.<\/p>\n
It\u2019s critical to know the size of particles in your cleanroom for manufacturing, but also for certification. Cleanroom Certification requires a concentration of particles to be below accepted limits of a sample volume based on the Class of Cleanroom, particle size tested and the Cleanroom operation based on the number of HEPA filters, type of filter, and the number of air changes per hour.<\/p>\n
2.\u00a0\u00a0Anatomy Of A Particle Counter\u00a0<\/strong><\/span><\/pre>\n
We use light scattering to detect and size particles. But it\u2019s not a perfect science. That being said, it\u2019s the best technology we have to date. So as you decide on where to source your particle counter or where to service it, make sure they are the ones setting industry standards and best practices.<\/p>\n
Particle counters house a laser sensor block inside them that does the processing of the particles. This block contains the following elements:<\/p>\n\n\n\n
\n
    \n
  1. Laser diode<\/li>\n
  2. Sample inlet<\/li>\n
  3. Sample exhaust<\/li>\n
  4. Sample view volume (the area where particles pass through the laser and scatter light)<\/li>\n
  5. Sensor cavity & optics<\/li>\n
  6. Photodetector<\/li>\n<\/ol>\n<\/td>\n
\"\"<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
These components allow the particle counter to move air through the sensor block and detect the size of the particle through light scattering.<\/p>\n
3. Fundamental Methods Particle Counters Use To Collect & Size Particles<\/strong><\/span><\/pre>\n
Now that we know and understand what the inside of a particle counter looks like, we can recognize how the air is brought into the particle counter for evaluation. This is the key to understanding the fundamentals of particle counters.<\/p>\n
Through the use of a pump, a vacuum is created that pulls in air from outside the particle counter. That vacuum pulls the air from the inlet through the laser diode and then out through the exhaust.<\/p>\n
As the air passes through the inlet, it\u2019s compressed so that we can get the most accurate light scattering reading possible.<\/p>\n
When it passes through the diode, it reflects the light, causing light scattering. The larger the particle, the more light is reflected.<\/p>\n
That\u2019s where the photodetector comes into play.<\/p>\n
The photodetector is what converts the light energy into a voltage signal. This way, we are able to quantify the physical size of the particle and present a particle count! Those are the fundamentals of how a particle counter works.<\/p>\n
4. Want a real-world example of a similar physics phenomenon?<\/strong><\/span><\/pre>\n
Think of the air like a half-full bucket of water.<\/p>\n
You know there is half a gallon of water in the bucket.<\/p>\n
When you place a bowling ball inside the water, the water level rises to \u00be of the bucket. You know there\u2019s no more water than before in the bucket, but now it looks like the bucket has \u00be of a gallon of water \u2013 because the volume of the water was displaced.<\/p>\n
Using a trusty\u00a0formula<\/strong><\/a>\u00a0from high school physics, you could calculate the object\u2019s volume that displaced that volume of water.<\/p>\n
The same principle applies in light scattering: we can tell the size of the particle by the amount of light displaced.<\/p>\n
5. Where Particles Come From In A Cleanroom<\/strong><\/span><\/pre>\n
If everything is working correctly, you shouldn\u2019t be seeing many particles at all in your cleanroom. But they do get in there! How?<\/p>\n
Personnel are the highest source of contaminants in cleanrooms, accounting for 75% to 80% of particles found. We shed skin, hair, and microorganisms constantly \u2013 even when we are sitting.<\/p>\n
We shed about 40,000 skin cells\u00a0every minute<\/strong><\/em>.<\/p>\n
Even when we are stationary, we generate about 100,000 particles of 0.3 microns or larger.<\/p>\n
When we\u2019re moving, that number increases to more than 5,000,000.<\/p>\n
(That\u2019s a lot of potential contamination if guidelines are not strictly adhered to.)<\/p>\n
Our gowns even have contamination \u2013 so the antiseptic gowning protocol is important. Often, people don\u2019t gown properly, leaving skin around the wrist exposed. This is a huge risk within a cleanroom as bacteria and viable particles can be introduced into the environment.<\/p>\n
While you\u2019re in the cleanroom, the way you move and expose yourself is also incredibly important. Particles can even get through gowns so they are not guaranteed to protect the cleanroom from a person\u2019s contaminants.<\/p>\n
If the FDA or external auditors come into your cleanroom, the first thing they will do is check your personnel and the way they interact with the cleanroom.<\/p>\n
So where else do particles come from?<\/p>\n