Hybrid Filters

Hybrid filters are a type of air filter, which incorporate two or more filter control technologies. They may combine the mechanical filters with an electronic filters in an integrated system or single self-contained device. Like mechanical filters, they contain a type of filter media as well as like the electronic filters they have the ability to charge the particles in the air and collect them in charged collection plates.

The filters inside the hybrid filters can be replaced just like a mechanical filtering system. Their efficiency is very good as they are able to handle a lot of airflow. They are capable of removing different types of unwanted and harmful particles from indoor air.

Types of Hybrid Filters

• Electret Media Filter: Electret media filter is a type of hybrid filter. It uses a permanently charged media, which is fabricated into either flat panel filters or extended media filters. The media filter, made from synthetic fibers, is inherently charged in the manufacturing process and it retains the charge which attracts airborne particles that are snared and retained within the fibers in the formal methods of impingement and diffusion of other dry-type filters. As the filter becomes more soiled, the resistance to airflow increases gradually. Therefore the filter must be replaced periodically.
  
  The main advantages of an 'electret' filter are their relatively low energy cost and high efficiency when clean. However the disadvantages are high maintenance costs as they are frequently needed to be replaced and their efficiency that drops with use.
  
  

Ionizing Charged-Media Filters:

Another category of hybrid filters is ionizing charged-media type filters. This type of filter works differently as dust in the air is initially charged and then it is collected on a charged-media filter.

Their mode of operation is very simple. They charge the particles in the air with negative or alternating negative and positive charges. Charging of the particles enhances their deposition in conventional extended-media high-efficiency filters. The advantages of such systems are that they decrease the particulate counts in the occupied space, enhance the performance of the particulate filters, and diminish the housekeeping costs of particle soiling in the space. The main disadvantage is that its initial equipment cost is high and far above the cost of conventional high-efficiency filters.

• Electrostatically Enhanced Filters: Electrostatically enhanced filters are another category of hybrid filters. In this type of filter, an electric field is superimposed on the fibrous, media-based air filters. The principle behind this technology is electrostatic precipitation superimposed on other capture mechanisms, like sedimentation, diffusion, impaction. However, they aren't largely popular as they aren't commercially available. But under experimental conditions, this technology has proved to increased filtration efficiency, compared to media-based filters alone.