This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. Designation: E679 - 19 INTERNATIONAL Standard Practice for Determination of Odor and Taste Thresholds By a Forced- Choice Ascending Concentration Series Method of Limits This standard is issued under the fixed designation E679; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. Anumber in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. INTRODUCTION The obtaining of odor and taste thresholds requires the sensory responses of a selected group of individuals called assessors. These thresholds may be determined in order to note the effect of various addedsubstancesontheodorandtasteofamedium.Theymayalsobedeterminedinorderto characterize and compare the odor or taste sensitivity of individuals or groups. It is recognized that precise threshold values for a given substance do not exist in the same sense that values of vapor pressure exist. The ability to detect a substance by odor or taste is influenced by physiological factors and criteria used in producing a response by the assessor. The parameters of sample presentation introduce further variations. Thus, the flowrate of a gaseous, odorous sample has an influence on the detectability of an odor. However, a concentration range exists below which the odor or taste of a substance will not be detectable under any practical circumstances, and above which individualswithanormal senseof smellortastewouldreadilydetectthepresenceof the substance. Thethresholddeterminedbythispracticeisnottheconventionalgroupthreshold (thestimuluslevel detectable with a probability of 0.5 by 50 % of the population) as obtained by Practice E1432, but ratherabest estimatenotfartherefrom.Thebias of the estimatedepends onthe concentration scale steps chosenandonthedegreetowhicheachassessor'sthresholdis centered withintherangeof concentrations they receive. The user also needs to keep in mind the very large degree of random error associated with estimating the probability of detection from only 50 to 100 3-AFC presentations. 1. Scope 1.5 This practice describes the use of a multiple forced- 1.1 This practice describes a rapid test for determining choice sample presentation method in an ascending concentra- tion series, similar to the method of limits. sensory thresholds of any substance in any medium. 1.6 Physical methods of sample presentation for threshold 1.2 It prescribes an overall design of sample preparation and determination are not a part of this practice, and will depend on a procedure for calculating the results. the physical state, size, shape, availability, and other properties 1.3 The threshold may be characterized as being either (a) of the samples. only detection (awareness) that a very small amount of added 1.7 It is recognized that the degree of training received by a substance is present but not necessarily recognizable, or (b) panel of assessors with a particular substance may have a recognition of the nature of the added substance. profound influence on the threshold obtained with that sub- stance (1).2 1.4 The medium may be a gas, such as air, a liquid, such as water or some beverage, or a solid form of matter. The medium 1.8 Thresholds determined by using one physical method of may be odorless or tasteless, or may exhibit a characteristic presentation are not necessarily equivalent to values obtained odor or tasteper se. by another method. 1.9 This international standard was developed in accor- dance with internationally recognized principles on standard- 1This practice is under the jurisd