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Method of Judgment
Measurement values of the three gases are compared with 'Cognitive thresholds'. If the
value is above the threshold, ‘+’ is given. If it is below the threshold, ‘-' is given. 'Cognitive
threshold' is the lowest level of concentration where people can identify what kind of smell it
is. As there are differences between individuals in the level of the olfactory sense, it should
be regarded as a
“
guideline.”
The combination of ‘+’ and ‘-' is compared with the judgment patterns and the one with the
same combination is the judgment given.
There are seven judgment patterns as follows:
No.
H
2
S
CH
3
SH
(CH
3
)
2
S
Judgment sentence
1
-
-
-
Sulphur compounds are not present in this sample. Breath
odors may be present from products other than sulphur
compounds – e.g., lactic or acetic acid.
2
+
-
-
Hydrogen sulphide will contribute to breath odor in amounts
close to or over base line.
3
+
+
+ or -
All
three
sulphur
compounds
are
present.
These
compounds, if present in sufficient amounts, will combine
and contribute to breath odour.
4
+
-
+
Hydrogen sulphide and dimethyl sulphide, if present in
sufficient amounts, will combine and contribute to breath
odour.
5
-
+
-
Methyl mercaptan can contribute to breath odour if present
in amounts close to or over baseline.
6
-
+
+
Methyl mercaptan and dimethyl sulphide, if present in
sufficient amounts, will combine and contribute to breath
odour.
7
-
-
+
Dimethyl sulphide is a cabbage-like odour that bacteria
commonly produce. It can sometimes be digestive in origin.
The default 'Cognitive thresholds' and ‘Judgment sentences’ have been specified. The
values and contents, however, can be changed on “
System settings
” window.
