Pocket filters are filters used in

HVAC Heating, ventilation, and air conditioning (HVAC ) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. ...

applications to remove

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

from ambient

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

. They are commonly used as final filters in commercial applications or as

prefilter In mathematics, a filter on a set X is a family \mathcal of subsets such that: # X \in \mathcal and \emptyset \notin \mathcal # if A\in \mathcal and B \in \mathcal, then A\cap B\in \mathcal # If A\subset B\subset X and A\in \mathcal, then B\in ...

s for

HEPA filter HEPA (, high efficiency particulate air) filter, also known as a high efficiency particulate arresting filter, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standa ...

s in hospitals in the

Pharmaceutical Industry The pharmaceutical industry is a medical industry that discovers, develops, produces, and markets pharmaceutical goods such as medications and medical devices. Medications are then administered to (or self-administered by) patients for curing ...

. Pocket filters were historically produced from

glass fiber Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...

media, however in recent a years a shift to synthetic media took place. Glass fiber media is prone to

bacterial growth 250px, Growth is shown as ''L'' = log(numbers) where numbers is the number of colony forming units per ml, versus ''T'' (time.) Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providi ...

and shedding. On the other hand, it has the advantage of increased filtration efficiency over time. Synthetic media filters are usually

electrostatic Electrostatics is a branch of physics that studies slow-moving or stationary electric charges. Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word (), mean ...

ally charged to increase efficiency. The drawback of this approach is the media loses efficiency by as much as 75% over time. To remedy this manufacturers have introduced new multilayer synthetic media with a smaller fiber

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

. Not only does this approach contribute to a limited loss of efficiency, but also to a

service life A product's service life is its period of use in service. Several related terms describe more precisely a product's life, from the point of manufacture, storage, and distribution, and eventual use. Service life has been defined as "a product' ...

that is longer by more than 30%. Some filters come with bacteriostatically treated media to prevent bacterial growth, while others come with a media that is inherently not suitable for bacterial growth. Pocket filters come with a pocket number of 3–12 depending on the frame size. Frame material can be Metal of Plastic. The most common frame sizes are: * * * * Despite the advances in synthetic media, pocket filters are slowly being overtaken by rigid type filters made from glass fiber paper or more recently from

nanofiber Nanofibers are fibers with diameters in the Nanometre, nanometer range (typically, between 1 nm and 1 μm). Nanofibers can be generated from different polymers and hence have different physical properties and application potentials. Examples ...

. These filters usually offer a service life that is 4–8 times what is offered by pocket filters at a lower energy expenditure.

References

{{reflist Filters