How To Estimate the Odour Control Unit Capacity?

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Whether we’re talking about chemical storage tanks, lagoons of slurry or food manufacturing, we design every odour control system to achieve a measured removal rate in ouE/m3. Additionally, every odour control system has a flow rate measured in m3/hr, which lets us calculate the system’s treatment capacity.

This article will explore these odour control measurements so you can estimate the odour unit capacity and removal rates of your systems.

Odour control unit capacity

Odour control systems process a maximum airflow volume measured in m3/hr (cubic meters per hour). We estimate m3/hr requirements based on the operational capacity of the plant/site.

Another unit of measurement is ouE/m3 (One European Odour Unit per hour), which is the number of odorants evaporated into one cubic metre of gas. ouE/m3 sets the target for the odour removal efficiency, defining outlet concentration.

Understanding m3/hr

Simply, m3/hr is how many cubic metres of air the odour control unit will process in an hour. A higher m3/hr means it has a higher capacity.

However, a higher capacity is not always desirable, especially in smaller systems, because a higher capacity means a more extensive, more complex system, which increases cost. Thus, finding a balance between capacity and size is crucial.

A standard odour control unit has a capacity of 50 m3/hr to 1,000 m3/hr, which sounds like a lot. Still, it is nothing relatively speaking – OSIL’s CCU (Containerised Carbon Unit) treats 6,000 m3/hr to 45,000m3 /hr with a stackable design.

The ability of an odour control system to treat airflow volumes depends on four key factors:

•  System size

• Adsorbent selection

• Adsorptive capacity

• Process conditions – temperature, chemical constituents, moisture

There is more to satisfying a required m3/hr than pumping lots of air through an extensive system; the odour control system needs to treat the air effectively and achieve a desired ouE/m3 (odour concentration).

Understanding ouE/m3

Simply, ouE/M3 is how we measure odour control unit capacity. It is an objective measure of odour concentration (the amount of odour).

All odour control systems take contaminated air gas and treat it mechanically, chemically, or biologically. ouE/M3 can be measured before and after treatment to determine the efficiency of odour removal.

OSIL and most other odour control experts use ouE/m3 because it is the European standardised method of conducting olfactometry. It accurately tells us the concentration of odours, so we can measure removal rates and efficacy.

In odour monitoring and olfactometry, ouE/m3 measurements are usually described with the following notation:

C98, 1-hour = x ouE/m3 w

• x: Limit concentration in ouE

•1-hour: the average time the concentration is calculated

• 98: the percentile that is used to derive concentration value

This notation is used in odour monitoring to define odour concentrations, allowing us to measure tiny concentrations. This is helpful when designing mitigation measures and fine-tuning the performance of odour control systems.

Find out more

Want to find out more about odour control solutions? Contact us today and speak with one of our experts. Just call +44 (0)1543 506855.

How To Choose the Right Odour Control Technology?

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To choose the right odour control technology, first, we need to identify the types of odour you produce and the concentration of the odours.

Many processes produce predictable odorous compounds as by-products, like hydrogen sulphide and ammonia. However, we still need to figure out the makeup of the compounds to choose the right odour control solution.

Odour monitoring and sampling

For existing processes, we use odour monitoring, a scientific process that detects and collects data about odours such as concentration and type.

The following data sets are useful:

  • F – Frequency
  • I – Intensity
  • D – Duration
  • O – Offensiveness
  • L – Location / R – Receptor

Techniques for acquiring data include olfactometry, which requires physical sampling and analysis in a lab, instrumental odour monitoring systems (electronic noses that collect data and send it to a control centre) and the human nose using trained experts.

Odour sampling and analysis is taken further by Gas Chromatography-Mass Spectrometry (GC/MS), which tells us the gas components at a molecular level. GC/MS is crucial when odours are complex and not easily identifiable.


Pre-build processes 

For pre-build processes, odour control should be built into the process to integrate the technology and solution fully.

When specifying odour control systems for new processes, we consider the types and concentrations of odours that are predicted to be produced, air and flow rate, available site space, maintenance requirements and treatment location.

We know what technologies work for odours through experience and fieldwork, not to mention the vast scientific research over the years. Your build will have specifications, so we’ll specify technologies that meet your demands.

Available technologies

Once we know more about the odours you produce, we can look at specifying technologies that will deal with them. Here are a few available technologies:

  • ChemKlean (wet scrubbing) – Removes odours from air gas streams using a liquid chemical absorbent. Specified for basic odour control applications like inlet works. 
  • LavaRok (biofiltration) – A biological filter made from pumice stone with bacteria that turns biodegradable compounds into food.
  • Tube vents and a passive filter – Specified for vent gases and tanks to absorb hydrogen sulphide and other noxious odours produced in sewage treatment.
  • OdaCompact (two-stage treatment) – Two stages of odour treatment in a single tower, combining LavaRok biofiltration with CuCarb dry media filters
  • CCU (Containerised Carbon Unit) – A stackable, containerised odour control system that uses activated carbon adsorption with CuCarb filters.  

Localised vs centralised odour control

Sometimes, the right technology setup depends on the floorplan of the site, with site space also a factor in sizing and specifying odour control systems.

Localised odour control includes several smaller odour control systems located close to the emission source, eliminating complex pipes and ductwork.

Centralised odour control includes ductwork to move contaminated air into a central, large odour control system, which can be located externally.

For multi-stage treatments, we can also combine localised and centralised odour control. In this setup, localised systems might scrub non-organic odorous compounds to prepare the air gas stream for final polishing in a larger biological system.

Speak to one of our odour control experts today to find out more about how we size and specify the right odour control solutions for our customers.

Get rid of odours at petrol and fuel refineries


Petrol and fuel refineries produce a variety of odorous compounds including sulphides, mercaptans and hydrocarbon compounds.

These refinery odours can seep into the atmosphere and cause nuisance complaints, damaging the refinery’s reputation.

Inevitably, completely getting rid of petrol and fuel refinery odours isn’t possible – like all odours, we can only control and manage them.   

Thankfully, petrol and fuel refinery odours can be efficiently dealt with using modern filtration systems that remove, absorb and adsorb odorous compounds.

Such systems need to be properly sized and specified for the application, but first, it is necessary to analyse odours and monitor them so that we can evaluate odour problems and devise accurate, efficient and effective solutions.

Odour monitoring

Data logging

Odour monitoring involves using sensors to monitor the sources of odours so we can evaluate the extent and types of odour produced. Armed with this information, we can at least offer basic advice on appropriate solutions.


Olfactometry is an in-depth, lab-based odour analysis that detects and measures key odour-generating compounds. It measures the concentration of odours with an odour number that determines the strength of the odour.


Gas Chromatography Mass Spectrometry (GC-MS)

GC-MS combines gas chromatography (which tells us the various components of an odour) with mass spectrometry (which tells us the mass-to-charge ratio of one or more molecules present in a sample), giving us an odour breakdown.

Odour control systems

To get rid of odours at petrol and fuel refineries, we can use a variety of odour control systems in either single or multi-stage treatment processes:

Passive filters (adsorption)

High-quality ‘passives’ offer effective hydrogen sulphide and VOC removal. Oil and chemical storage tanks, vents and containers are prime applications.

Our passive filters have a disposable/refillable filter, and the carbon media can be tweaked to remove different odours. For example, impregnated carbon can be used to remove NH3 (ammonia) with high efficacy.

Passive Filters and Tube Vents

Dry scrubbing (adsorption)

OSIL’s activated carbon dry scrubbers offer effective hydrogen sulphide, VOC and ammonia removal at high flow rates. Dry scrubbers are a good solution for petrol and fuel refineries that produce significant volumes of organic odours.

Our dry scrubbers can operate as a single standalone unit or as a polishing unit downstream of biological or chemical treatment systems.

Dry Scrubbing

Wet scrubbing (absorption)

Wet scrubbers remove contaminants from air gas streams with a liquid absorbent (water with chemical additives). Our ChemKlean® Scrubbing System can be utilised for inlet works and exhaust gases for petrol and fuel production processes.

Wet scrubbing is often paired with a biological treatment, or the OdaCompact® system, a space-saving system that combines LavaRok® biofiltration dry media.

Wet Scrubber

Biological systems (degradation)

Biotrickling filters and biofilters are two types of biological system that use a biomass to remove organic compounds from air gas streams.

Our systems use LavaRok® for the media bed. The big benefit of LavaRok® biofiltration for refinery odour control is it produces no contaminated sludge as a by-product, so it significantly reduces waste.

Biological System

Providing odorous compounds are biodegradable, biological systems will treat large volumes of air with excellent efficiency.

Biological treatments can be used in refineries to remove odours from gas flaring systems, bitumen production and septic water areas.

Find out more

If your refinery is looking into odour control solutions, contact us today for a chat about how we can help you meet your goals.

9 Reasons Why Odour Monitoring is Crucial


Odour monitoring is a scientific process that aims to detect and collect data about problem odours such as intensity and type. It is crucial in industrial and commercial odour control for a variety of reasons. Here are the 9 main reasons:

  • It empowers every odour management plan

Odour monitoring will form a crucial part of your odour management plan. With it, we can answer questions like which processes are performing well, where you might need to act, and how to reduce odour emissions to a fraction of their size.

  • It is necessary to detect and measure odour-generating compounds

Odour monitoring is necessary to detect and measure odours so that we can make odour management decisions based on data, not guesswork. Without this data, everything would be a guess, leading to poorly specified equipment.

  • It is necessary to size and specify the correct odour control solutions

It’s only possible to size and specify the correct odour control solutions once we know what types of odour we are dealing with. Odour monitoring is a necessary first step to determine what odour controls need to be put in place.

  • It prevents over engineering and investment in the wrong solutions

It isn’t uncommon for businesses to invest in odour control equipment that isn’t precisely what they need. This is due to a lack of data. Odour monitoring provides precise odour data, so that correct investment decisions can be made.

  • It is necessary to correctly abate industrial odours

The successful abatement of industrial odours is necessary if businesses are to comply with regulations and avoid odour complaints. Real-time odour monitoring enables businesses to keep tabs on odours so that inefficiencies are logged.

  • It can act as an alarm system in case of accidental odour release

Continuous odour monitoring utilises sensors (electronic noses) that can detect odour leaks with configurable tolerances and feed this data to a control centre. If there is an accidental odour release, the system will provide an alert.

  • It enables site managers to act fast if there is a leak

If you don’t act fast in the event of an odour problem, you could generate complaints and that small issue could get worse. With continuous odour monitoring, you can consistently detect odour control problems and act immediately.

  • It reduces nuisance complaints

Real-time odour monitoring helps to reduce nuisance complaints by giving you time to resolve issues before they generate complaints. Electronic noses can be used to detect high levels of odour escaping out into the atmosphere.

  • It enables changes to operations that improve odour control

Perhaps the biggest benefit to odour monitoring is it enables management to make good decisions for potential changes to operations and new site developments related to odour control. Solutions can be designed, rather than thrown in.

Find out more  

Getting a correct picture of your odour levels is key to making sure that any odour removal solutions are appropriately specified. Email us at or call us on +44 (0) 1543 506855 to discuss your odour monitoring needs.

How Odour Monitoring, Sampling and Analysis works?

How Odour Monitoring, Sampling and Analysis works

When odour management decisions are based on nothing but guesswork this often results in incorrectly specified odour control systems.

This shouldn’t come as a surprise. After all, how could anyone select and size the correct odour control system without knowing anything about the odours? That would be like trying to fix a car without  understanding the problem!

The solution to collecting the necessary data is odour monitoring, sampling and analysis, which will provide a full picture of the scale of your odour problems.

Emission measurement is crucial to the control of odours. Before you can define the extent of an odour problem, you need first to identify the potential sources of any odour emissions and understand their magnitude and characteristics. By defining and characterising what odours are being produced by your business, we can also ensure you invest in the right odour control system.

Odour Monitoring

Odour monitoring is a scientific process that aims to detect and collect data about odours such as concentration and type. The FIDOL method is a common monitoring technique. This collects the following types of data:

  • F – Frequency
  • I – Intensity
  • D – Duration
  • O – Offensiveness
  • L – Location / R – Receptor

Odour emissions are typically measured in European odour units in accordance with the EN13725 European Standard for olfactometry, or as individual chemical components using compound specific detectors or molecular analysis. Olfactometry is the preferred approach for environmental odours which are generally mixtures of different odorous components.

It requires the collection of samples  which are analysed  at an accredited laboratory and the level of information it provides is unequalled. This technique can provide a complete picture of your odours.

Electronic noses (also known as instrumental odour monitoring systems) are another option. These devices are strategically deployed on-site. They collect real-time data and send it wirelessly to a control centre for analysis.

Data loggers are also widely used close to sources of Hydrogen Sulphide (H2S) emissions to collect data about frequency, intensity and duration. We use on site data loggers to detect and measure key odour-generating compounds.

Odour Sampling and Analysis

Odour sampling involves collecting odour samples from multiple sources so they can be analysed. This data allows us to measure and evaluate odours.

Odour Sampling

Odour samples can be collected in several ways, including vacuum containers attached to a pump, sampling hoods and sampling bags.

The most accurate tool for analysing odour samples is Gas Chromatography Mass Spectrometry (GC/MS). This identifies the components of a gas at a molecular level, giving us a scientific picture of the odorous compounds.

Samples collected for Olfactometry need to be sent to an accredited lab for analysis. We can collect the necessary samples and arrange analysis which   speeds up the time to get the results.

Sampling and analysis is necessary to classify odours and evaluate the odour control technologies that would be most effective. Combined with our odour expertise, we can develop a full picture of the scale of your odour problems.

Want to know more about odour monitoring, sampling and analysis? Speak to one of our odour experts today about how we can help you.