Chemical filters for gases

A chemical filter takes gases out of the air. It binds them to the filter medium by a chemical reaction. The medium is made of small porous grains of alumina. They are treated with a substance that reacts with the gas. Such a filter captures gases that pass straight through a dust filter. In the trade this is also called molecular filtration or gas-phase filtration.

Next step: Ask for advice on the medium

How does chemisorption work?

The gas reacts with the substance in the grain and stays there. The odour or harmful gas is changed into something else. It is not just held for a while. Plain activated carbon works in another way. It holds compounds by a physical bond, and that bond can be undone. Chemisorption mostly cannot be undone. Activated carbon can also be impregnated. Then it binds gases both ways.

The impregnation depends on the gas. An acid gas needs an alkaline impregnation. An alkaline gas needs an acid one.

Which gases a chemical filter binds

Which of these gases a medium binds depends on the impregnation. For gases around electronics, see Corrosion protection.

An example from the range is alumina balls of 2 to 5 mm with 4 per cent potassium permanganate (KMnO4). That medium is meant for H2S, SO2, SO3, formaldehyde, ethylene and mercaptans, among others.

Filter types

• Filter cartridges and filter modules. For standard applications. A perforated cartridge can be filled with chemical media or with activated carbon.
• Filter boxes and panels. For larger capacity.
• Custom media. Blends and impregnations matched to your gases.

Chemical media are also used in air handling units and vent filters. See Filter installations.

Do you already have media housings? Then a medium can be chosen that does the same job. The housings can stay where they are.

How the medium is chosen

The choice depends on how fast the air flows and how much gas it holds. It also depends on how long the gas must be in contact with the medium. In a modular filter unit from this range, the residence time is at least 0.10 seconds per filter bed.

For advice we need the same data as for any gas filter. That is the gases and how much of each, the air flow, the temperature and humidity, and how long the filter must last. With that data you can request a quote right away.

Where chemical filters are used

Chemical filters are used in data centres and labs, for example. They are also used in the pharmaceutical and petrochemical industries and in waste plants. In data centres and technical rooms they protect electronics from gases that cause corrosion. See Corrosion protection. For switch rooms and MCC rooms we have a separate site: corrosion in technical rooms.

When does the medium need replacing?

When the impregnation is used up. A lab can test a sample of the medium. It shows how many days the medium will still last. See Measurements and analyses.

Frequently asked questions

Absorption or chemisorption: what is the difference?

In absorption, a gas dissolves in a liquid, as in a scrubber. In chemisorption, the gas reacts with a solid medium and stays bound to it.

Does a chemical filter also work against odour?

Yes. Odour often comes from H2S or ammonia. A chemical filter binds those gases. For odour from VOCs, plain activated carbon is mostly the choice. See Activated carbon filters.

Request a quote

Name the gases you know of, the air flow and the room where the filter will go. Don't know which gases are there? Then the gases, and how much of each there is, can be measured. See Measurements and analyses.

Next step: Request a quote