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Odor Investigations

June 3rd, 2008

Odor InvestigationsNuisance odors are a complex and subjective issue, often resulting in odor complaints directed at industrial or agricultural facilities such as wastewater treatment plants, landfills, large scale composting facilities, or animal feed operations. At these types of facilities, most odorous chemical compounds are produced under anaerobic conditions. Contrary to popular belief, nuisance odors themselves do not generally cause long term illness or any direct health effect.  In other words, if the source of the odor is taken away, any associated illness symptoms (e.g. nausea) will also go away. Therefore, unlike investigations centered on human health risk, investigations involving nuisance odor are governed by the perception of the receptor. A person’s perception of odor is related to the human olfactory system, which can vary widely from person to person; what smells bad to one person might not have an odor at all to someone else. To further confuse the issue, there is a distinct lack of odor regulations, and those that exist are extremely vague. The EPA defaults to the state level for nuisance odors, and most states defer to the county or local level.

Odor is a parameter which may be measured unto itself, following established ASTM and/or European Standards. This approach will quantify how odorous a sample is, ranking it on a relative scale with units of dilution to threshold (D/T).

Knowing the magnitude of an odor problem is useful, but often more detailed chemical information is necessary when odor control engineering solutions are being evaluated.  When a detailed chemical analysis of odorous compounds is needed, there are several analytical options:

1. Produced during the acidogenesis stage of anaerobic digestion, reduced sulfur compounds have a very characteristic odor of rotten eggs, rotten garlic/cabbage, skunk or natural gas. In fact, the human nose is sometimes more sensitive than the most current analytical instrumentation used to detect these compounds. An example of these compounds is methyl mercaptan, which has an extremely low odor threshold (this is why mercaptans are used as natural gas odorants). The most popular analytical option for reduced sulfur compounds is ASTM Method D5504. This method quantifies a list of 20 speciated reduced sulfur compounds (such as hydrogen sulfide, mercaptans, thiophenes) using gas chromatography with a sulfur chemiluminescence detector (GC/SCD).

2. With a characteristic fishy/fertilizer or putrid/sour/pungent odor, amines are the result of the biological breakdown of amino acids and are produced at various stages of anaerobic digestion. Columbia Analytical has developed a comprehensive amine sampling and analytical method that reports a list of 13 amine compounds with reporting limits at or below published odor threshold concentrations. A sample is collected on an in-house designed sorbent tube using a personal sampling pump. Due to their unique chemical characteristics, amines will not always be detected in any of the other tests described here (e.g. VOC test). Analysis of the samples is via a specially modified gas chromatography with nitrogen phosphorous detection (GC/NPD).

3. Ammonia, which is produced by microbial decomposition of animal waste, has a characteristic odor most people will recognize due to the compound’s use in window cleaners. At higher concentrations, ammonia can cause serious health damage, irritating and/or burning nasal passages and lungs. Collection of airborne ammonia may follow the OSHA ID-188 method, which uses sulfuric acid-coated Anasorb-747 (carbon bead) tubes and a personal sampling pump for collection. This means of sample collection is much easier and safer than the traditional collection technique of sulfuric acid solution impingers. Analysis may follow the OSHA-ID 164 analysis, which utilizes an ion-specific electrode (ISE) to detect ammonia.

4. Carboxylic (volatile fatty) acids are produced as a result of the biological anaerobic breakdown of proteins, with typical odor characteristics including a rancid, fecal, vomitous, or sweaty gym sock smell. Columbia Analytical has developed a comprehensive sampling and analytical method that reports a list of 15 carboxylic acid compounds with reporting limits at or below published odor threshold concentrations. The sample is collected on a sodium hydroxide-treated silica gel tube using a personal sampling pump; the subsequent sample is then analyzed via gas chromatography/mass spectrometry (GC/MS).

5. Several other analytical methods may be used to quantify levels of aldehydes and other miscellaneous volatile organic compounds (VOCs). EPA Method TO-11A (silica gel tubes coated with acidified 2,4-dinitrophenylhydrazine (DNPH) ) is an appropriate method for sampling of aldehydes (carbonyl compounds).  EPA Methods TO-15 (stainless steel canisters) and TO-17 (thermal desorption tubes) are appropriate methods for sampling of volatile organic compounds.  Polar volatile compounds such as alcohols, aldehydes, esters, ketones, ethers, phenols and cresols are often contributors to nuisance odors.

Due to their complex nature, there is no “one size fits all” approach for evaluating the chemical composition of odors. Odorous compounds may have additive, synergistic or antagonistic effects, all contributing to odor perception. Multiple analytical methods or evaluation approaches may be required to address a single source.

Learn more about Odor Testing

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11 Responses to “Odor Investigations”

  1. Steve McCollum Says:

    Superb! As an entrepreneur I know that “cash is king.” And only second to that is “Knowledge.” I appreciate your Odor Investigation discussion.



    Could you give me the ASTM and european standards , so that I can order.
    I look at method development from you.

    Mitra Ramlakhan
    Environmental Engineer

  3. Alyson Fortune, Columbia Analytical Services Says:

    Some of the main ASTM/European Methods for evaluating odor in a sensory manner are:

    ASTM International E679-91″Standard Practice for the Determination of Odor and Taste Thresholds by a Forced-Choice Ascending Concentration Series Method of Limits”

    ASTM International E544-99 “Standard Practice for Referencing Suprathreshold Odor intensity“

    EN 13725:2003 “Air Quality – Determination of Odor Thresholds by Dynamic Dilution Olfactometry”

  4. Johnson Khor Says:

    Thanks for the wonderful article.

    I think it will be easy to tell what compound that caused the odour, if the odour just caused by common gas specifies. Example: If easy to distinguish how is the ammonia & H2S smell like.
    But if we have the odourous air sample that caused by VOC. Even can use GC-MS(screening) to analyse the sample, but is ready hard to identify which exact compounds that resposible for the odour.

    My question:
    1) Is they any possibility that the various VOC will react with each other and convert to another kind of VOC and make the new odor/smell that not so easy to be recognised.
    That mean : If we have 10 ppm IPA and 20ppm butyl acetate encounter in the air . What would be the smell like? Will be IPA smell like, butyl acetate smell like or IPA + Butyl acetate smell.


  5. Columbia Analytical Services Says:


    There is always the possibilty of chemical interaction between constituents resulting in compounds of unknown odors. Trying to characterize the odor of the new compound would be challenging. In most cases our sweep of methods can isolate those compounds that have created the odor. I agree that common compounds such as ammonia and H2S can be easily identified by their distinct smell but in the presence of hydrocarbons it can mask the odor readily. Our methods are very specific to those class of compounds and can identify the compounds through the background. Hope this helps.

  6. Sunni Says:

    We have just discovered the presence of Carbonyl Sulfide and Carbon Disulfide in our home but have no clue where it is coming from. It isn’t present when all the windows and doors are closed; it is activated when a door and window is open. There is rarely an odor outside and it is always inside when there is ventilation. Any ideas?

  7. Alyson Fortune, Columbia Analytical Services Says:


    In selected past odor investigation projects, our lab has seen both carbonyl sulfide and carbon disulfide related to products such as wallboard and silicone rubber. Those two components are also known low level artifacts in tedlar bags. Carbonyl sulfide can also be seen in propane and other natural gas products, since it is formed via hydrolysis in the presence of hydrogen sulfide (rotten egg smell) and carbon dioxide; however, if the source of these contaminants were from some type of natural gas/propane, I would expect to also see other natural gas odorants present as well (e.g. methyl mercaptan, tetrahydrothiophene).

  8. Ravi Says:


    Thanks for the wonderful article.

    I was looking for a solution to my problem of masking smell of IPA when I came across your article. The staff complain about it when they use IPA as a cleaning solvent. I am going to try adding pine oil or camphor. Please suggest any other product, preferably some thing volatile which evaporates with IPA.



  9. Jane Says:

    Spray Foam Insulation has a growing cohort of homes that emit chemical and fishy smells long after the proposed cure rate of 2-3hrs. Some home are 3 years and still odorous. Heat and Humidity tend to increase the odors. Occupants are dealing with headaches, asthma, skin rashes ect. Isocyanates are not found in air sampling but amines seem to be present, but other chemicals of unknown identity are also being found. Side B of the SPF is largely (70%) ‘trade secret’. Should the owners of these homes be concerned for their health? Is it possible the trade secrete is dangerous and if so how can a lab identify these chemicals?

  10. Nicole Pannone, Columbia Analytical Services Says:

    Hi Jane,

    Thanks for your interest.
    As a lab, we can’t speculate on the possible health risk for the home owners or on the composition of the “trade secret.” That would be up to a risk assessor or an indoor air quality specialist.
    As to how we could identify these chemicals – it’s possible that an air sample could be collected with either a sorbent tube or a Summa canister, and the resulting sample analyzed by GC/MS following either EPA TO-17 or EPA TO-15. If this is something you’d like more information about, we’d encourage you to call the lab and discuss the investigation in a bit more detail with one of our project managers.

  11. Linda Says:

    I am seeking guidance on odor monitoring for our social responsiblities in tobacco production requierments. We are a tobacco dealer, buying, conditioning, and packing. We are required to monitor odor. There are no current regulations that I can go to for guidance. I have looked at ASTM-E544-99. Really good stuff but over our heads in this industry. Anyone else had to monitor this?

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