Filter Bag Micron Ratings ExplainedOne micron is a unit of length equal to one millionth of a meter, using the symbol: μm.
Filter micron levels specify the average size opening in the filter media. If a polyester fiber filter bag is rated for 20-micron filtration, the average size opening between fibers is 20 micron.
Typically, filter media is given a micron rating based on an 80% efficiency, meaning that the filter will remove 80% of contaminants greater than 20-micron if you are using a filter bag rated for 20 micron.
Nominal vs Absolute Micron Ratings
Most filter bags are rated with what’s called a “nominal” micron rating, meaning that a percentage of particles larger than the specified micron rating will pass through the bag. An “absolute” micron rating will filter 99.9% of particles at the specified micron rating.
Absolute-rated bag filters are significantly more expensive when compared to a nominal-rated bag filter. For most applications, using a nominal-rated filter bag allows for users to achieve the desired end result or product at a much more affordable cost.
Approximate Micron of Common Materials
|Particle Size in Microns|
|Coffee||4 - 400 *|
|Corn Starch||0.1 - 0.8 *|
|Clay (coarse)||2 - 4 *|
|Clay (medium)||1 - 2 *|
|Clay (fine)||0.5 - 1 *|
|Dust Mites||100 - 300 ****|
|Fertilizer||10 - 1000 *|
|Gelatin||5 - 90 *|
|Gravel (very fine)||2000 *|
|Gravel (fine)||4000 *|
|Gravel (medium)||8000 *|
|Gravel (coarse)||15000 - 30000 *|
|Gravel (very coarse)||30000 - 65000 *|
|Ground Limestone||10 - 1000 *|
|Human Hair (diameter)||70 ***|
|Lead (solder radiator manufacturing)||1.3 *|
|Lead (battery and lead powder manufacturing)||12 - 22 *|
|Lead Dust||0.1 - 0.7 *|
|Mold||3 - 12 *|
|Mold Spores||10 - 30 *|
|Naked-Eye Visibility||40 ***|
|Pollen||10 - 1000 *|
|Red Blood Cell||12 **|
|Sand (fine)||250 **|
|Sand (beach)||700 **|
|Sea Salt||0.035 - 0.5 *|
|Silt (coarse)||37 *|
|Silt (medium)||16 - 30 *|
|Silt (fine)||8 - 13 *|
|Silt (very fine)||4 - 8 *|
|Spores from Plants||3 - 100 *|
|Starches||3 - 100 *|
|Sugars||0.0008 - 0.005 *|
|Tea Dust||8 - 300 *|
|White Blood Cell||25 ***|
** H20 Warehouse.com: https://www.h2owarehouse.com/info-micron.htm
*** INDUSTRIAL SPECIALTIES MFG. & IS MED SPECIALTIES (ISM): https://www.industrialspec.com/resources/mesh-and-micron-sizes/
**** Commercial Filtration Supply: https://www.commercialfiltrationsupply.com/education/a-better-understanding-of-micron-ratings.html
For more information on bag filters, read our Bag Filter FAQs or speak with a PRM Filtration expert today.