Prevention is preferred to other controls. If possible, capture and destroy odors before they are released to the environment. If prevention or destruction is not possible, dispersion may help to avoid problem odors. Most of the controls are physical controls. There are also legislative controls.
Some examples of legislative controls include the following:
Restricting operating times of day
Odor complaints often occur at certain times of day. Odor diaries may be one way to identify the worst times of day or week for odors. It may be helpful for the odor-producing facility to shut down or reduce the odor-producing operations during the time(s) of day/week when the odors are worse.
Local authorities can determine where (locations) odors are worse and prevent future odor-producing additions such as upgrades, new construction, new industry, etc. through zoning restrictions.
Some examples of physical controls that involve destruction and dispersion include the following:
Reduce emissions through use of odor control technologies. More information can be found in the following section and from EPA’s Technology Transfer Network Clean Air Technology Center:
A summary of common technologies is listed below.
Reduce emissions by planting trees or structural barriers between the odor producing area and communities.
Control Technologies for Point Sources
Odor control technologies have been developed for point sources. An example of a point source is manure storage in an enclosed barn.
Use afterburners or catalysts placed in the process line or stack to destroy odorants prior to release. These technologies are widely available, very effective and commonly used to reduce emissions of hazardous air pollutants.
Absorb odorants into a liquid solvent. Similar to incineration and typically used in a stack, this technology is commonly used to reduce emissions of hazardous air pollutants and is very effective and widely available.
Adsorption or Dry Scrubbing
Pass the gaseous stream through a material such as carbon in a bed or filter to remove odorous gasses. The gas molecules of an odorant are captured on a solid surface. Adsorption technology is very effective and widely available.
Biofilters and Chemical Filtration
Run the gaseous stream through a large bed of soil, compost or peat and let microorganisms living in the medium metabolize and degrade odorants as they pass through. Biofilters are effective and relatively inexpensive.
Control Technologies for Area Sources (For example Open Manure Storage Lagoons)
A floating permeable cover can control odors from storage lagoons and can also control microbial growth by providing a large surface area biofilter.
Control Technologies for Both Area and Point Sources
Release odorants through a high stack causing dilution of the odorants before receptors are exposed. The use of minimum separation distances between an odor source and receptors is an effective control method if adequate separation distances exist or if a facility has a large stack.
Add additional odorants or substances into the atmosphere to change the perceived intensity or character of an odor. An odor modifier can be a masking agent, a counteractant or a neutralizer. The effectiveness of this control method is uncertain and would be limited to specialized situations.
References and Resources
EPA’s Technology Transfer Network Clean Air Technology Center available online at
SRF Consulting Group Inc. A Review of National and International Odor Policy, Odor Measurement Technology and Public Administration. SRF Rep. no. 0034734. Minneapolis: Minnesota Pollution Control Agency (MPCA), 2004. Print.