A Guide to Micron Ratings In Industrial Filtration

The micron scale is used for extremely fine technical measurements, but it’s also become something of a popular buzzword – leaving many to wonder, “Exactly what is a micron?” In this guide, we will explain the definition of a micron, and how filtration material with micron and sub-micron ratings are used within the industrial filtration market.

The Micron Scale

A micron – short for “micro-meter” and denoted µm – is one-millionth of a meter (0.00 0001 m), or more usefully, one-thousandth of a millimeter (0.001 mm). For industrial applications, this scale of measurement is most useful to capture extremely fine dust, oily or waterborne particulates, and airborne vapors using unique, precision-engineered filtration materials.

How Small Is a Micron?

1 micron is well below the limit of visibility, which is around 40 microns for most people.

To put that into perspective, the smallest bacteria and mold spores reside at a level between 2 and 10 microns, and the smallest water-borne micro-plastics identified are just under three microns. This means that a one-micron filter can possibly remove 100% of the most common particulate from a liquid or air.

To better visualize the incredibly small sizes involved, consider how a single micron compares to the following*:

• 5 µm – Bacteria
• 7.5 µm – Red blood cells
• 10 µm – Smoke
• 25 µm – White blood cells
• 30 µm – Mold spores
• 75 µm – Human hair
• 90 µm – Pollen
• 125 µm – Table salt

(*Approx. measurements)

It’s hard to fathom, but if something the size of 1 µm were enlarged to fit in the palm of your hand, a square meter enlarged by the same order of magnitude would grow to just under 50 sq. miles – i.e., it would compare to a baseball laying on the ground in the middle of New York state.

Technically accurate engineering at this extreme level of scale requires incredibly painstaking exactitude and consistency – but the rewards include extremely refined industrial filtration techniques that give global industries much greater ability to process materials and achieve major improvements in a facility’s safety, sanitation, efficiency, and product quality.

Micron Filtration

By operating at these phenomenally small scales, filtration materials with micron and sub-micron pores are perfect for industries that rely on advanced filtration techniques in order to manage their product flow, control pollutants, and keep certain materials separated from others.

Commonly known for its use in reverse osmosis liquid filtration, micron filtration can also be applied to:

• Dry materials
• Various chemicals
• Ultra-fine dust and aerosols
• Gasses & vapors
• Oily substances

As we will discuss in the next section, the properties of the substance(s) being filtered are what primarily determines the type of material and design requirements of industrial micron or sub-micron filters.Micron filtration is one of the most advanced methods yet known for filtering sub-microscopic particulates. This is achieved with extremely tightly woven fabrics, PTFE membranes, and other materials, which may be further treated for even greater control over the filtration process. For example:

• Innovative fabric finishes and surface treatments may be applied to fabrics with micron-sized pores if their filtration capacities need to be enhanced. These finishes also prolong the lifespan of the filter and help prevent it from becoming blinded.
• Our proprietary Unipore expanded PTFE membrane surface can repel moisture, water-borne acid, alkali substances and oils. The result is that only the intended substance is filtered, even when it is mixed together with other substances (as is most often the case).

How To Determine the Right Micron Rating

Often, new customers ask if a higher or lower micron rating is required. The correct micron rating depends on the manufacturing process and expected outcomes. With this information, the technologists can determine the necessary micron rating in strict accordance with the filter’s purpose. Consider three of the most common scenarios:

1. There may be times when it is necessary to allow larger substances through a filter. Using unnecessarily small pores may slow the process down outside of the system’s flow rate requirements and create adverse effects.
2. It is not uncommon to have multiple filtration stages with unique requirements. This is useful if larger-particulate substances are separated prior to sending the rest of the substance to the next filtration stage, where smaller particles can be filtered for a secondary purpose.

This wide range of options is possible due to the availability of micron- and submicron-level engineering achieved by leaders in the industrial filtration industry. When determining the micron rating needed for your industrial filtration needs, start first with the size and qualities of the particulate requiring filtration.

How To Determine the Required Properties of the Media

This will vary widely depending on the industry in which you are involved – using the automotive oil industry as an example, you will need to understand the size of the particulate you are filtering

• 75 microns: Heavy motor oils (up to 70-weight)
• 45 microns: Multi Viscosity oils and medium-weight motor oils (not exceeding 50-weight)
• 35 microns for extremely low-weight oils (e.g., 10/20, 10/40)

The properties of the particulate determines what the micron rating is required of the filtration media:

• Filter bags are commonly used for dry applications 
• Fluid bed dryer bags are used to dry powders
• Filters treated to repel certain substances, but capture others for filtering substances with multiple property dynamics (e.g., oily and containing fumes)

Other reasons filters might require special treatments are, as mentioned, to extend filter life and prevent the filters from blinding.

Superior Filtration Solutions

With over 70 years of experience, we are at the leading edge of industrial filtration solutions. At Filter Holdings, our experienced team works closely with our clients to create industrial filters with nominal micron ratings customized to the clients’ exact purposes. For the tightest filtration needs, contact the Filter Holdings team to find the appropriate filter solution for your micron and sub-micron filtration needs.