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At 3M Filtration Products, our approach to air filtration is simple: create an obstacle path to stop as many particles as possible, while still allowing air to flow freely through the filter. The result is a line of air filtration materials and products suitable for most applications and flexible enough to fit almost any design.
Our products use several filtration mechanisms to clean the air. In most cases, particles larger than 10 microns drop out of the airstream before reaching the filter due to gravitational settling. Large particles are also captured through sieving, because they are simply too large to fit between the fibers of the filter. In addition, our products also use the following capture mechanisms: |
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Inertial impaction: Larger particles bump into the filter fibers because they cannot follow the airstream as it moves around the fibers.
Direct interception: Intermediate-sized particles are captured as they follow the airstream around the filter fibers, whenever the airstream comes within a halfparticle diameter of the fiber.
Brownian diffusion: Particles smaller than 0.1 micron are bounced around by the motion of the air molecules, causing the particles to come into contact with the filter fibers.
Electrostatic: Fibers are given permanent electrical charges to attract any particles in their vicinity, which greatly increases the "electret" filter's ability to capture small- or medium-sized particles.
Submicron particles are difficult to capture, even using a combination of mechanical methods. For that reason, many of our filters use electrostatic capture mechnisms for maximum efficiency against the most penetrating particles.
At 3M Filtration Products, we offer a number of filtration options:
Filtrete™ Air Filter Media - electret filter media which attains high efficiencies primarily through electrostatic attraction (as well as through mechanical capture methods)
3M Brand Microfiber Filter Media - electret filter media which relies mainly on Brownian diffusion, inertial impaction and direct interception to capture particles in higher airflow situations:
3M Brand Microporous Polypropylene Membrane - membrane which uses sieving action to attain extremely high efficiency against submicron particles. |
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We Use 3M Technology To Make A Better Filter Top of Page |
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A prime example of electrostatic enhancement in action is our Filtrete™ Air Filter Media. Each and every nonconductive fiber contains permanent, electrostatic charges that enhance particle capture efficiency. With its patented electret construction, Filtret media captures particles throughout the media, rather than mostly on the media surface. |
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The result is efficiencies up to 99.9999%, depending on the application - with demonstrated high efficiency against difficult-to-capture, submicron particles. It is best designed for use when high efficiency is needed with low pressure drop. Because we have created electrostatic fibers that are so efficient in capturing particles, we are also able to give Filtrete media a more open construction. Air molecules encounter fewer fibers as they pass through the filter, resulting in extraordinarily low-pressure drops and greater air flow.
The low-pressure drop is maintained during use because Filtrete media is a three-dimensional, depth-loading filter rather than a surface-loading filter.
Although the use of electrostatics is not uncommon in filtration, Filtrete media is superior for three reasons:
- it provides the highest charge density of any electrostatically charged material;
- these permanently charged rectangular fibers provide more loading surface than do round fibers; and
- the charged media is combined with depth filtration to provide a higher loading capacity.
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