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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Health Care and the Importance of Air Quality Control

Nowhere is air filtration more important than in a health care facility. The level of airborne infectious contaminant increases proportionately with the increased population density of infected individuals. Concern is not limited to hospitals, as many invasive procedures are now performed at outpatient facilities. Additionally the congregation of people endemic to these facilities increases the likelihood of contaminant transfer. Other types of health care facilities that have a need to control air quality for health include nursing homes and dental offices or clinics.

Various authorities have established guidelines for levels of air filtration in health care facilities. Guidelines recognized within these recommendations include the United States Department of Health & Human Services (DHHS), the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), and the Centers for Disease Control & Prevention.

Air filters offer excellent protection from the airborne maladies of health care facilities, as long as they are a component in an overall program of air quality control. Components include air filters, the air filter housings or holding frames, air changes supplied to the conditioned space, temperature and humidity control, outside air introduction and appropriate control of airflow to protect visitors from undue exposure. Some patients, such as those in burn wards require additional considerations for their protection.

The protection of facility employees is also a paramount concern. Clinical staffs are subject to increased exposure to infected individuals. Support personnel are also subject to exposure. Proper application of air filtration and proper engineering controls can reduce the risks by a level of magnitudes. Additionally, those that service the engineered air systems require engineering expertise and should be educated as to the importance of the systems that they maintain.

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