Air Filter Media Fiber Size Dictates Performance

Two types of media are available in today’s high efficiency air filtration market, coarse fibers (synthetic) and fine fibers (microfiber glass). Coarse fiber media, larger in fiber size, incorporates electrostatic attraction which is introduced as part of the manufacturing process. Fine fiber media includes fibers that are extruded to a smaller fiber diameter to incorporate the filtration principle of diffusion. Both medias will also strain particles from the airstream, although this principle only has a value when the offending particles are above 2-micron in size. Coarse fiber media will drop in overall efficiency as the filter loads with contaminate and dissipates the charge or insulates the fiber from the air stream. Fine fiber media will increase in efficiency over the life of the filter. The scanning electron microscope photos at the right show coarse fibers and fine fibers at 400X magnification. Note the finer fiber diameter of the Hi-Flo® micro glass filter fibers.

The chart above shows filter performance after a short period of operation in a system. Although both tested filters are rated MERV 13 when evaluated under ASHRAE Standard 52.2 the coarse fiber filter shows a significant drop in particle capture efficiency wherein the Camfil Farr Hi-Flo using fine fibers increases in efficiency as the filter operates within the system.

Given that 99% of all particles are under 1-micron in size, which filter would you like to see in your HVAC system?

In reality, when all factors are considered, fine fiber filters have a lower life cycle cost. Contact Camfil Farr, or your local Camfil Farr Distributor or Representative for a life cycle cost analysis.

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