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Odors and Emissions

The Odor Assessment Laboratory studies air emissions for the development of improved agricultural management strategies.

Odors and Agriculture

  • Agriculture is a key industry in Pennsylvania.
  • Odors are an unavoidable consequence of animal agriculture.
  • Rural population growth and expanding animal operations are increasing nuisance odor complaints.
  • Agricultural odors are a complex mixture of many compounds (odorants).
  • The human nose, the ultimate odor sensor, is capable of detecting thousands of odorants.
  • Selected odor characteristics can be objectively quantified.
  • International protocols assure that odor study results are reproducible.
  • Odor mitigation practices can be used to reduce off-site nuisance situations.
  • Odor research strives to assess the effectiveness of alternative odor mitigation practices.

The Penn State Odor Assessment Laboratory

  • Adheres to rigorous international protocols for human odor panel testing.
  • Specializes in human sensory methods to characterize and quantify odors.
  • Employs state-of-the-art dynamic olfactometry equipment for odor panel assessment.
  • Employs the only university-based forced-choice dynamic olfactometer in the Mid-Atlantic region dedicated to the study of agricultural odors.
  • Employs portable olfactometry equipment for field odor measurements.
  • Uses a variety of laboratory-based and field gas collection techniques.
  • Offers supplimental gas measurement methods for quantification of ammonia and greenhouse gas emissions.

Nuisance Odor Factors

  • Odor Factor WheelFrequency
  • Intensity
  • Duration
  • Character
  • Hedonic Tone


Environmental odors are characterized using the Odor Character Description Wheel.

Odor CharacterOdor Character Wheel

  • Floral
  • Fruity
  • Vegetable
  • Offensive
  • Fishy
  • Chemical
  • Medicinal
  • Earthy

"Earthy" Descriptors

An "earthy" odor character has the following descriptors.

  • Ashes
  • Chaulk-like
  • Grassy
  • Mold
  • Mouse-like
  • Mushroom
  • Musky
  • Musty
  • Peat-like
  • Pine
  • Smokey
  • Stale
  • Swampy
  • Woody
  • Yeast

Olfactometry: Use of the human sense of smell to characterize and quatify odors.

Human Sensory Thresholds

Detection: observer can sense a difference in the air environment… air is different from odorless control.

Recognition: observer can assign a descriptive term to odor.

Olfactometer - Air Dilution Concept

Mixing of carbon-filtered air with odorous air.

Mixing carbon-filtered air with odorous air.

PDF, 967.9 KB

This document summarizes, in an easy-to-read format, current information on odor management for agricultural and food processing operations.