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Filtration Table of Contents | Air
Filter Suppliers
HVAC Filter Suppliers
Air filters of many types and materials of
construction have been designed, manufactured, and applied to
meet a wide variety of industrial and commercial requirements
for clean air (e.g., industry makes full use of all filter
types). Commercially available filters are divided into three
distinct categories based on how they operate to remove
suspended particulate matter from the air passing through
them. The largest category, often referred to as ventilation
or heating, and air conditioning (HVAC) filters, is composed
of highly porous beds of resin-bonded glass or plastic fibers
with diameters ranging from 1 to 40 micrometers (µm). The
fibers act as targets for collecting airborne dust. As their
name indicates, HVAC filters are widely used for air cleaning
in mechanical ventilation systems. They are almost all
single-use, disposable items, and are used in all sectors of
industry, including as pre-filters that reduce the amount of
coarse dust reaching more efficient filters located
downstream.
Typical HVAC filters:
Fiberglass Filter: Typically
manufactured using medium to heavy cardboard frame with
layered fiberglass reinforced with a metal mesh for support
from collapse. Used in most HVAC filtration
applications.
Polyester Filter Media Pad: Polyester offers
higher resistance and dust holding capabilities than most
fiberglass filters. Frequently used to replace fiberglass
filters, which can fragment and send fibers into
the air stream. Used in most HVAC filtration applications.
Electrostatic Filter: These filters create a
self-generated charge helping to collect dust
particles. These filters are typically manufactured
using multiple layers of polypropylene media or similar within a galvanized frame or cardboard frame.
A second category also is comprised of
single-use, disposable filters called HEPA filters. By
definition, a HEPA filter is a throwaway, extended-medium,
dry-type filter with: (1) a minimum particle removal
efficiency of no less than 99.97 percent for 0.3-µm
particles, (2) a maximum resistance, when clean, of 1.0
inches water gauge (in.wg) when operated at 1,000 cfm, and
(3) a rigid casing that extends the full depth of the
medium [Note: Filters of different flows and
resistances are allowable by the AG-1 Code. 2 A filter of
identical construction and appearance, but having a filtering
medium with a retention of 99.9995 percent for 0.1 µm
particles, is referred to as an ultra-low penetration aerosol
filter (ULPA). The filtering medium of HEPA filters is
thinner and more compressed, and contains smaller diameter
fibers than HVAC filters. HEPA filters are widely used
throughout industry.
A third category of commercial air filters is
known as industrial cleanable cloth filters. As the
designation indicates, these filters have built-in mechanisms
for periodically cleaning the filtering surfaces of
accumulated dust. Unlike the first two types, industrial
cleanable cloth filters rely on building a thick layer of
dust on the surface of the cloth to provide a high-efficiency
filtering medium. This type of filter is used in industry
involving high concentrations of coarse mineral dusts.
Further, this third category includes special
types of particulate filters for chemical and combustion
operations. These include deep beds of sand in graded
granular sizes, deep beds of glass fibers, and stainless
steel membranes formed from compressed and sintered granules
or fibers. Stainless steel membrane filters operate like
industrial cleanable cloth filters in that they depend on a
dust layer for high-efficiency particle removal and
must be cleaned periodically, usually by reverse compressed
air jets.
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