Passive Odour Control Units


Passive odour control units can be very useful to eliminate odours from smaller odour sources. In some situations like manholes, air relief chambers,… it is impossible to install a fan driven odour control unit. There might be no electricity available to run a fan or the OCU has to be installed below the street level. The activated carbon systems are commonly used in sewage applications for the removal of H2S. To enable the in situ regeneration of the carbon with water, these units contain catalytic activated carbon.


When passive odour treatment systems are installed, special attention is paid to the sealing of the chamber. All accesses, cable conduits, etc. must be fully sealed, allowing the foul air to breathe only through the carbon filter.

Ipec offers a wide range of passive odour control units
  • Manhole buckets will trap odours from sewage gravity lines before they escape to the surroundings. The buckets can be positioned under the manhole cover so there will be no visual disturbance . If an existing manhole is provided with a sealing plate, the manhole bucket can be integrated in the sealing plate. By reusing the corresponding sealing plate the air tightness is guaranteed.
  • Above ground passive units are used for several applications like vacuum pumps or air relief valves where foul air escapes discontinuously through venting. Note that the air that escapes is not diluted by fresh air which results in air flows with high odour levels and special care should be taken to the sizing of such systems.
  • Underground passive units: The complete unit can be installed underground. This can be done along the road side or if required even under the road, parking or any accessible area. For these heavy loading situations, Ipec designed a special two-wall GRP vessel with steel fibre reinforcement to allow the load of heavy vehicles on the underground unit. The underground unit does not cause any visual disturbance and it does not take any space above-ground. The system can be provided with a spraying system for in situ regeneration of the activated carbon.

All these passive units can be installed with a water spraying system in the vessel for regenerating of the water regenerable activated carbon.

Case story: IPEC – Passive Odour Control Unit