If your industrial operation generates noxious/toxic organic gases, passive filters are the simplest way to filter vent gases on storm, sludge, sewage and waste holding tanks, fume exhaust cupboards and pump sumps under positive pressure.
We typically specify passive filters when there is a need to vent otherwise noxious and unpleasant gases out into the atmosphere. We call these systems ‘passive odour control units’ because they are self-contained units.
OSIL is a leading provider of activated carbon-based, passive filters. We can specify the correct media for your use case. Our filters are disposable/removable and can be placed in the middle or at the top of the pipe stack.
How Passive Filters work
Passive filters are made from activated carbon. The contaminant removal process is adsorption; when contaminated air passes through the filter, certain gases react chemically with the carbon and stick to the media.
Due to the cavernous surface area of the activated carbon, the removal rate of organic gases with passive filters is extremely high. The carbon is extremely porous, so there’s a lot of surface area for the organic gases to cling to.
Passive filters are commonly used to filter the following contaminants:
- Hydrogen sulphide (H2S)
- Volatile organic compounds (VOCs)
- Ammonia (NH3) *Impregnated carbon needs to be specified for NH3. This is specially impregnated to remove ammonia from air gas streams.
Passive filter in industrial odour control
One of the big benefits of our passive filters is they can be disguised as inanimate objects, like bollards, lamp posts and trees. They can also be coated in any colour with textured and matte coatings, so they reflect no light and draw no attention.
The removal efficiency rate with passive filters can exceed 99%. This is dependent on the surface area of the filter, the specification of the carbon, and how contaminated the air is (the first two points are determined by the last point).
Here are a few examples of how passive filters are used:
- Food factories use passive filters on storage tanks and tube vents
- Pharmaceutical companies, laboratories and medicine manufacturers use passive filters for fume cupboards
- The oil and fuel industries use passive filters for vent gases on oil storage tanks and for vapour control in tube vents
- Wastewater and sewage treatment plants use passive filters for vent gases on storm, sludge, sewage and waste holding tanks
- Sewage pumping stations use passive filters on pump sumps under positive pressure so that pumping activities do not generate odour complaints.
Odours that cannot be controlled with broad spectrum media can be controlled with impregnated media, allowing passive filters to be used in many applications. The removal rate of passive filters is measured in ouE/m3.
Talk to OSIL about passive filters
We are a leading supplier of activated carbon-based passive filters and tube vents and we provide a low-cost, fast turnaround activated carbon resupply service. We can design your OCUs to treat a specified ouE/m3. Call us on +44 (0) 1543 506855 to find out more.