- You would miss out many web searches, multiple hours reflecting on conflicting information you've read and collected as well as wondering "am I really addressing the issue from the right angle"? Furthermore, why would you want to benefit from the knowledge of an odor expert, who has already worked with similar issues and is familiar with the current best practices and tools?
- Once your odor expert has produced an opitmized odor action plan, you would have to find some other projects to spend your budget dollars on.
- You would miss the "pleasant encounters" with angry neighbors and other stakeholders following an odor incident.
- Once the the odor expert had pinpointed problem sources and assessed their emission rates, you would miss the feeling of insecurity created by mysterious odor problems.
- You would miss all the running around trying this and that. Would you miss reviewing your action plan every other day? You may even find it boring having only a few short and long term odor abatement projects!
Maybe I am going to give an odor expert a call!
Why not call Odotech? Please contact us.
It is often said that odor measurement is subjective. This statement comes certainly because odor measurements are based on human odor panels that sniff the air to determine the presence of odor.
Odor measurement | Odor panel of an olfactometric analysis
It is likely also due to the variation in people's sensitivity to odor or personal appreciation of different odors.
Odor measurement is, as a matter of fact, a dose-response relationship evaluation of an odorant substance. The dose-response relationships are commonly used in pharmacology, toxicology, biology and medical science. No one would think that these sciences are subjective. Olfactometry (odor measurement) is based on the same sound science.
The dose-response relationship, or exposure-response relationship, describes the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor (usually a chemical) after a certain exposure time. This may apply to individuals (eg: a small amount has no observable effect, a large amount is fatal), or to populations (eg: how many people or organisms are affected at different levels of exposure). (Source: Wikipedia).
Dose response curve from an olfacomtetric analysis
In the case of odor measurement:
- the change in effect on an organism is the odor perception
- the differing levels of exposure (or doses) are the dilutions of odor
- the stressor is the odor
- the population sample is the odor panel.
An olfactometric analysis is an analytical test of odor quantification or measurement of the odor concentration (according to established protocols). The goal of an olfactometric analysis is to determine the odor perception threshold. By definition, the perception threshold is when 50% of the population detects an odor because of the presence of odorant chemical compounds. The Odor unit, is by definition, 1 o.u./m3, the odor perceived (but not necessarily recognized) by 50% of a panel (1 o.u./m3 corresponds to the detection threshold). The Odor concentration (number of odor units) represent the number of dilutions (with odorless air) of the gas mixture required to obtain 1 o.u./m3. The greater the number, the more "odorous" the sample is.
State of the art olfactometry will use panels that have been tested and selected according to the EN13725 standard and certified olfactometer operating in specific controlled conditions. This standard has been proven to provide reliable reproducible results.
It is absolutely valid to consider the odors subjective in terms of the appreciation of their quality. This belongs to the taste and experiences of each individual. On the other hand, the odor quantification is an objective method based on scientific fundamentals eliminating all the subjectivity related to odor perception.
Olfactometry is a great tool to translate into a quantitative and objective value the complexity of odor perception (see blog: Are odors additives in terms of the intensity?)
Dynamic dilution olfactometer
However, in some circumstances, real-time values are required to provide the dimension of odor fluctuations of a process that olfactometry can hardly provide. Indeed, olfactometric measurements require sampling and lab analysis that practically or financially limit the amount of values available to understand the odor fluctuations out of an odor source.
Let's take the example of a biofilter exit treating composting odors. In this case, the process generates pulsed air flow for windrow forced aeration.
What do we see here?
First, using today’s standard ‘manual’ odor sampling and measurement method (blue dots), we measure three separate odor concentrations at different points in time, then connect the dots to obtain rectilinear segments.
In this case, looking at a biofilter designed to limit odor output to 400 odor units, the ‘manual’ method (olfactometry) would indicate that the biofilter is working fine and the neighbors would perceive no odor. However, there are still odor complaints; no one knows why.
Then we install an electronic nose OdoWatch (magenta curve); this gives us continuous measurement; and we now see that there are odor peaks up to 750 odor units.
The mystery is solved. Now we can act to deal with the problem. Measuring daily average odor concentration may doesn’t work. The human nose senses peak values not average values. Thus the monitoring system needs to measure odor concentration at very short intervals. OdoWatch measures odors every second.
The scope of this blog post is to introduce odour impact assessment methodology for a pulp & paper plant. The original paper of this blog present the standardized methodology & technologies and typical results for each key step from a coated fine paper production plant: odour flow rates from point & surface emitting sources, overall sites odour flow rate, dispersion modeling results.
Pulp and paper plants involve major facilities, both large and complex. Odour emissions are difficult – even impossible – to manage without being able to measure them and to predict their impact. Hence, it is important to develop tools capable of measuring odour emissions objectively and estimating accurately their short-term.
Odour impact assessment is a very effective & objective method to quantify the magnitude and the area of such nuisances. Theses Odour Impact Assessment Studies (OIAS) have been carried out in many different industries with a comparable methodology. They include field odour samplings on point & surface sources, laboratory olfactometric quantification using the EN13725 standard, and dispersion modeling using local meteorological data. OIAS are used for appropriate Odour Master Planning and Monitoring Procedures that will prove long term improvements to stakeholders and the public.
METHODOLOGY USED FOR ODOUR IMPACT ASSESSMENTS
The methodology of an odour-impact study is very similar to the one for health risk analysis or environmental impact analysis. It is based on the characterization of the odorous sources, on the estimation of the odour concentration in a neighborhood and the exposure rate of the public. Next figure presents the main steps of the proposed methodology for OIAS. First, the main characteristics of the site must be compiled:
- Local environment data: meteorological data; type of environment: rural or urban, flat or hilly, etc.; human factors (population density and distribution, occupation, etc.);
- Source characteristics: emission types (stack, emitting area, etc.), source location and dimension, flow-rate and odour concentration.
Based on this information, the impact areas for the studies will be defined and an appropriate model for atmospheric dispersion of odours will be selected. Application of the selected model with meteorological and source inputs allows estimating odour concentration and/or public exposure frequency. At different stages in this methodology, information should be presented to the public, especially the conclusions of the OIAS, the proposed measures and the expected gain as well as the proposed monitoring plan. Participation of the public is a necessity to ensure acceptance of the plant/site continuing/future activities and to maintain a good relationship that may lower the number of complaints.
Three steps in the OIAS methodology require special considerations as they involve special techniques for odours:
- Source quantification,
- Dispersion modeling, exposure estimation and analysis,
- Odour monitoring.
They are discussed in this paper with the case study of a Coated Fine Papers Production Plant.
We are honoured to present you a special blog edition written by our guest author Dr. Johannes Frasnelli.
Dr. Frasnelli specialises in odor perception. He conducts research in the field of neurophysiology of smell and taste as well as therapy in loss of the chemical senses.
We have known for a long time that the occipital cortex is the brain region which is active if we are watching something; it is located in the very back of our brain. If we listen to music, on the other hand, the temporal region of the brain is active; this region is located just beneath the ear (interestingly, the left temporal region responds to sounds from the right ear and the right temporal region to sounds from the left ear). However, for a long time it was unclear with which part of the brain we smell, or, to put it into scientific terms, in which part of the brain olfactory information is processed. Over the last 30 years new imaging methods have become available which allow us to have a look at the brain at work, without harming the brain, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET).
Before fMRI and PET were available, researchers had to dissect the brains of dead bodies and follow the nerve bundles to see with which region the olfactory bulb was connected. But since PET and fMRI entered the stage we have gained much more insight into how our sense of smell works. The three most important brain regions are:
(1.) the orbitofrontal (from Latin: between eye-socket and forehead) cortex is located just above and behind our eyes;
Source: Paul Wicks
(2.) the insula (from Latin: island) is located deep beneath our ears;
(3.) the piriform (from Latin: pear shape-like) cortex is located just between the two other brain areas.
In addition, the olfactory brain includes smaller, but still very important brain regions (e.g., the anterior olfactory nucleus, the olfactory tubercle, the amygdala, and the entorhinal cortex). There are several interesting features related to the anatomy of the olfactory parts of the brain:
First, the olfactory regions do not only serve for smelling, but are also used, if we experience emotions and when we are memorizing events. This is the reason why odors can evoke very strong associations and memories of situations and place from a long time ago. Probably everyone knows an anecdote where he smelled a food or a perfume, and was brought back to early childhood and remembers exactly the circumstances of when he smelled that odor.
There is a second special characteristic of the sense of smell. For all the other senses (seeing, hearing, tasting, touching), the information from the sensory organs (the eyes, the ears, the skin, the tongue) travels through a brains structure called the thalamus (from Greek: room). The thalamus is something like a gate to our consciousness. If we focus on one sense (say, on vision while reading a very interesting book), we can blind out information from other senses (and not hear that someone was talking to us). This is done by the thalamus, who decides what we are aware of and what not. Since smell information is independent of the thalamus, we cannot blind out olfaction: we either smell an odor, or we do not smell it.
This particularity of not traveling through the thalamus is also responsible for another characteristic of the sense of smell. In all other sensory systems, a moderate (and for some even a light) sensation is enough to interrupt sleep: if we are asleep, a light, a sound or someone touching us is enough to wake us up. Unlike the other senses, a smell is not enough to wake us up; therefore we all have to install smoke detectors at home. If there is a fire, we would only wake up, if the smoke is so strong that it becomes stinging (and therefore is like a touch sensation). This may then be too late.
About the author: Dr. Johannes Frasnelli Ph.D.
Dr. J. Frasnelli is a graduate of the Medical Schools of the University of Vienna (Austria; 2001; Dr. med. univ.) and the Technical University of Dresden (Germany; 2009; Priv.-Doz.). Since 2006 he work in Montreal, first as an Academic Trainee at the Montreal Neurological Institute, since 2008 as a Postdoctoral Fellow at the Department of Psychology at the Université de Montréal. He currently hold a fellowship of the FRSQ. Dr. Frasnelli research interest is the neurophysiology of smell and taste as well as therapy in loss of the chemical senses.
Contact information: email@example.com