High Efficiency Gas Absorption "HEGA" Filter

HEGA is an acronym for "High Efficiency Gas Absorption". Originally developed by the British military as a defense against chemical warfare, HEGA is a carbon cloth filter. This carbon cloth has been claimed to be many times more efficient than the granular activated carbon form at adsorption of gaseous pollutants. With its light weight and easy workability, HEGA filters are now used in some residential air purifiers.

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What is a HEGA?
To be called a High Efficiency Gas Adsorber
(HEGA), the adsorber must exhibit a minimum
mechanical efficiency of 99.9% when tested in
accordance with the Institute of Environmental
Sciences designation: IES-RP-CC-008-84,
“Recommended Practice for Gas Phase
Adsorber Cell.” In addition, the adsorber must
be designed, built, filled and packaged in
accordance with the intent of this standard.
Since HEGA filters are manufactured in several
different sizes and of several different
materials, this standard is not always followed
to the letter. It is the intent of the standard and
the resulting performance of these adsorbers
that is important. This type of adsorber is not
intended to be used in odor control systems.
However, if the user needs a very efficient odor
control system and can justify the higher
initial and operating costs, then this type of
adsorber will do an excellent job. The following
comparison between an odor control type
adsorber vs. a HEGA may help:
An odor control type adsorber compared to
a HEGA is like comparing an ASHRAE type
particulate filter to a HEPA. The odor control
type adsorber (like the ASHRAE type
particulate filter) has a low efficiency, low
pressure drop and low cost. On the other
hand, the HEGA (like the HEPA) has a higher
efficiency, higher pressure drop and higher
cost. Both adsorbers have their place in
industry, but because of these major
differences they are not usually interchangeable.

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[FONT=times new roman,times]DESCRIPTION
Activated Carbon Cloth (ACC) was originally invented by the British Ministry of Defense for inclusion in chemical warfare suits. Today it has been developed for use in many odor control situations including industrial, medical, and domestic applications.

Zorflex® ACC has an extremely large surface area (1,000-2,000m2/g), being predominantly microporous. This, combined with the strong electrostatic forces developed within the cloth, enables the cloth to be highly efficient at adsorbing vapors and solvents.

Available in woven and knitted formats, the cloth is also offered in different activities, weights, and thicknesses. The cloth can also be impregnated with chemical treatments to make it more sensitive to adsorption of particular inorganic molecules.

FEATURES
Zorflex® ACC have several properties which explain their superior performance in a wide range of applications:
• As the material is 100% activated carbon, the cloth’s performance will exceed that of an equivalent weight of conventional carbon loaded paper, non-woven or foam, due to their lower carbon content.
• The flexible textile form offers superior handling in filter and product manufacture and makes lamination or bonding to other materials possible.
• This form of activated carbon cloth exhibits more rapid reaction and adsorption kinetics compared with granular activated carbon. Zorflex® ACC filters are therefore more effective when short contact time, high airflow speeds or small bed depths are required.
• A greater amount of vapor will be adsorbed by Zorflex® ACC compared with the same weight of granular activated carbon. Therefore Zorflex® ACC filters will be more effective in high vapor concentrations or where smaller bed depths are required.
• Zorflex® ACC’s high efficiency and large capacity for adsorption are less adversely affected by preadsorbed moisture than granular activated carbon. Therefore Zorflex® ACC filters are more suitable for use in humid environments where their effectiveness will be maintained.

APPLICATIONS FOR WOVEN CARBON CLOTH
• Oil mist filters in compressed air
• Gas sensor protectors and filters
• Protection of artifacts from tarnish and degradation
• Water purification
• Air purification
• Escape masks
• Low weight reduced resistance respirator canisters[/FONT]

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