Douglas W. Hamilton
Waste Management Specialist
Biosystems and Agricultural Engineering
Making Sense of Smells
A Guide for Understanding Farmstead Odors
Part 5: Odor Intensity and Offensiveness
Odor Measurement
How does it smell?
How Strong?
Charcter
Intensity
Two Methods for Intensity
1. Referencing Suprathreshold
2. Descriptive Category Scale
Referencing Suprathreshold
Odor Intensity
Odors are compared to
standards of known intensity
Referencing Suprathreshold
Odor Intensity
Odors are compared to
standards of known intensity
using dilutions of 1-Butanol
Referencing Suprathreshold
Odor Intensity
Odors are compared to
standards of known intensity
using dilutions of 1-Butanol
CH3CH2CH2OH
Referencing Suprathreshold
Odor Intensity
Port
www.rka-inc.com
1
2
3
4
5
6
7
8
Purdue Agricultural Air Quality Laboratory
Referencing Suprathreshold
Odor Intensity
Port
1
2
3
4
5
6
7
8
vol/vol 1-butanol
ppm
www.rka-inc.com
12
24
48
96
194
388
775
1,550
Purdue Agricultural Air Quality Laboratory
Referencing Suprathreshold
Odor Intensity
Port
1
2
3
4
5
6
7
8
vol/vol 1-butanol
ppm
12
24
48
96
194
388
775
1,550
www.rka-inc.com
Referencing Suprathreshold
Odor Intensity
Port
1
2
3
4
5
6
7
8
vol/vol 1-butanol
ppm
12
24
48
96
194
388
775
1,550
www.rka-inc.com
Referencing Suprathreshold
Odor Intensity
Port
1
2
3
4
5
6
7
8
vol/vol 1-butanol
ppm
12
24
48
96
194
388
775
1,550
www.rka-inc.com
Referencing Suprathreshold
Odor Intensity
Results reported in ppm 1-butanol
Referencing Suprathreshold
Odor Intensity
Port
1
2
3
4
5
6
7
8
vol/vol 1-butanol
ppm
12
24
48
96
194
388
775
1,550
www.rka-inc.com
Referencing Suprathreshold
Odor Intensity
Results reported in ppm 1-butanol
Intensity = 105 ppm 1-butanol
Referencing Suprathreshold
Odor Intensity
Results reported in ppm 1-butanol
Log10Intensity = 2.02 ± 0.267
N = 12
Descriptive Scale Odor Intensity
Panel rates Intensity
on a scale independent of
an external standard
Descriptive Scale Odor Intensity
1. Dilutions of odor are presented to
panel.
www2.dpi.qld.gov.au/environment
Descriptive Scale Odor Intensity
1. Dilutions of odor are presented to
panel.
2. Panelists rate odor intensity on a
descriptive scale.
Intensity Scale
0 = no odor
1 = very faint
2 = faint
3 = distinct
4 = strong
5 = very strong
6 = extremely strong
Descriptive Scale Odor Intensity
1. Dilutions of odor are presented to
panel.
2. Panelists rate odor intensity on a
descriptive scale.
3. Statistics are performed to
determine consensus of the panel.
Intensity vs Concentration
www.library.thinkquest.org
Measured Swine Odor Relationship
6
Odor Intensity
5
6 = Extremely strong
5 = Very Strong
4 = Strong
3 = Distinct
2 = Faint
1 = Very Faint
0 = No Odor
4
3
2
1
0
1
10
100
1000
Odor Concentration (OU)
Misselbrook, et al. 1993
Intensity vs Offensiveness
www.library.thinkquest.org
Odor Measurement
How does it smell?
How Strong?
Charcter
Intensity
Odor Measurement
How Good or Bad?
How Strong?
Hedonic Tone
Intensity
Odor Measurement
How Bad?
How Strong?
Offensiveness
Intensity
Offensiveness is an Intrinsic
Property of an Odor
A odor will be equally offensive,
no matter how strong.
Offensiveness by Olfactometry
1. Equal Intensity samples are
presented to panel.
www2.dpi.qld.gov.au/environment
Offensiveness by Olfactometry
1. Equal Intensity samples are
presented to panel
2. Panel rates offensiveness on a
descriptive scale.
Offensiveness Scale
0 = Inoffensive
1 = Very faintly Offensive
2 = Faintly Offensive
3 = Definitely Offensive
4 = Strongly Offensive
5 = Very Strongly Offensive
6 = Extremely Offensive
Offensiveness by Olfactometry
1. Equal Intensity samples are
presented to panel
2. Panel rates offensiveness on a
descriptive scale.
3. Statistics are performed to
determine consensus of the panel.
Measuring Farmstead Odors
Character
Persistence
Concentration
Intensity
Notes
Odors
Verbal Description
Offensiveness
Top Note
Middle Note
Base Note
Detection Level
Recognition Level
OU
Intensity
Intensity
Measuring Farmstead Odors
Character
Persistence
Concentration
Intensity
Notes
Odors
Verbal Description
Offensiveness
Top Note
Middle Note
Base Note
Persistency
Detection Level
Recognition Level
OU
Intensity
Intensity