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Activated Carbon

Activated Carbon
Jaime Graymead
July 6, 2017

Activated Carbon Filters – Panels and Discarbs

Carbon panels are normally supplied and fitted with an aluminium frame and can be made to any reasonable size to match existing panels of all makes. The depth of panel is restricted by our own imposed limits of not less than 10mm and not greater than 60mm Actual depth.

Capacities shown for Panels & ‘Discarb’ units are based on a dwell time of 0.1 seconds, which is the normally accepted minimum for most applications.

Air Flow = Width x Length x Depth/Dwell Time

or Air Flow = Width x Length x Face Velocity

As a guide,

Nominal thicknessActual thicknessPressure dropFace velocity m/s
25mm22mm45 Pa0.22 (43fpm)
22mm19mm40 Pa0.19(37fpm)

For ‘heavier’ odours i.e. Indian cooking odours, a contact time of 0.3 seconds is recommended, which will effectively reduce the Face Velocity and rating to one third.

Where hot air is being filtered (e.g. extract from cooker hoods) the carbon cells should be positioned as far from the heat source as possible.

Air stream temperatures must be maintained below 40Deg C. and humidity levels below 80% RH.  If temperatures or humidity in excess of either of these figure are anticipated, the airstream must be treated to ensure compliance.  Additional fresh air, and or cooling may be considered as suitable measures.

Pre-filters should be fitted in the ventilation system to protect the carbon filters in all installations from particulate contamination. We do not consider a glass panel to be suitable and recommend a filter having a minimum grade of F5 to EN779.

Some cooking operations give off large amounts of smoke, which is extremely detrimental if allowed to reach the carbon filters (smoke is a particulate).

In most cases this can be overcome by the use of a good quality pre-filter. e.g. an F8  Grade Bag Filter or better, depending upon circumstances. In some instances a HEPA Filter grade H14 is necessary.

’Discarb’ Cells can be ‘tailor-made’ to any reasonable size to fit ducting, air-handling units etc.

Activated carbons are graded as follows :        

Grade 20 Activity Carbons are rated 30% on their ability to ‘adsorb’ carbon tetrachloride (CTC) in testing; and have a typical surface area per weight of between 700-800 m2/g by the BET N2 method (the area being a measure of the area of the walls of the cavern like structure of the activated carbon): Bulk density is between 0.55 – 0.59 g/cc

Grade 50 Activity Carbons are rated 55% on their ability to ‘adsorb’ carbon tetrachloride (CTC) in testing; have a typical surface area per weight of between 1100-1200 m2/g by the BET N2 method (the area being a measure of the area of the walls of the cavern like structure of the activated carbon): Bulk density is between 0.49 – 0.53 g/cc.

Activated Carbon Panel Filters are generally manufactured using the bonding process to provide a rigid panel which is often called a “Biscuit”.  The bonded carbon biscuit can be framed in a metal channel so that it can be easily slid into channel holding frames mounted into ductwork or filter housings. The panel is finished in a “fabric facia” which minimises the dusting from the panel.

Activated Carbon Panel Filters can also be produced using a loose fill technique, which can offer an improved rate of absorbency.  Despite the improved rate of absorbency the Activated Carbon Panels capacity will remain the same  The panels are designed to minimise the risk of bypass due to settlement, and for this reason their installation should be designed to be horizontal.

activated carbon panel filters bonded

The metal cased ‘Discarb’ cells have the highest carbon loading in our range, and have standard or heavy-duty carbon panels permanently sealed into a galvanised sheet steel casing.

This construction gives a very strong unit capable of handling large air volumes or where conditions dictate, increased contact time. The advantage of this unit is that with panels sealed in, there is no possibility of air leakage.

Activated Carbon Discarb Filter Units can be manufactured to almost any reasonable size, the limiting factors being the overall weight for handling purposes and the size of individual panels.  When the unit has finished its useful life it is discarded and replaced with a complete new cell.

Lead Time

Activated Carbon Filters are manufactured to order at our works, and generally take 7-10 working days.