What is a micron rating and what does it mean for a filter?
A micron rating is commonly used to infer some type of level of filtration efficiency. However, with no industry, SAE, or ISO standard, there is no universal, apples to apples, methodology for the determination or reporting of a “micron rating.” It is important to know that a micron is a term for a linear unit of measure equal to one millionth of a meter. Put in perspective, a human white blood cell is about 25 mm in diameter. The Filter Manufacturers Council of MEMA has an excellent Technical Bulletin (TSB 89-5R3) that covers this topic in detail. To quote from TSB 89-5R3, “A filter that is marked or rated ‘10 micron’ has some capability to capture particles as small as 10 micrometers. However, when you see a filter marked ‘10 micron,’ you do not know exactly what this means unless you also have a description of the test methods and standards used to determine the filter rating. The results from the different test methods may not be comparable as their methodology varies greatly.” The
