2.2 气味的定量表达方法 The quantitative expression of odor

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2. 气味强度 Odor Intensity (strength)

气味是一种 “精神物理”现象。所感觉到的气味的强度随气味的浓度变化而变化。如下面的史蒂文定律所示,理论上,气味的强度是与气味的浓度呈指数倍变化的关系;Odor is a psychophysical phenomenon; the perceived odor intensity changes with concentration. Apparent odor strength (odor intensity) grows as a power function of the stimulus odor. S. S. Stevens showed that this power law (Steven’s Law) follows the equation:

I = k Cˆn

在上式中 Where

I 代表气味的强度;I is the odor intensity,

C 代表气味物质的物质浓度(如mg/m3);C is the mass concentration of odorant (i.e. milligrams/cubic meter, mg/m3),

k和n 代表不同气味物质所特有的常数;k and n are constants that are different for every odorant

 

在实际操作中,气味的强度是用标准气味物质-丁醇的百万分比(PPM)来表示。这个丁醇的值越大意味着气味越强,但它们不是简单的数字比率关系。The odor intensity value is expressed in parts per million (PPM) of butanol. A larger value of butanol means a stronger odor, but not in a simple numerical proportion.

空气中的气味强度能被客观地测量出来,这种客观的测量方法就是“气味强度参照尺度”(OIRS) [ASTM E544-99]。气味强度参照法,就是让训练有素的工作小组来比较空气中的气味强度与“标准参照气味物质”的一系列浓度的气味强度,最常用的“标准参照气味物质”是正丁醇。

气味强度可以用气味强度尺度来表示,它是用一种对气味感应的口头描述,而用数字表达出来。气味强度可分为下面的几个等级:

0 - 无味

1 - 非常弱(气味阀值)

2 - 弱

3 - 一般

4 - 强

5 - 非常强

6 - 无法忍受

Odor intensity of the ambient air can be measured objectively using an "Odor Intensity Referencing Scale" (OIRS) [ASTM E544-99]. Odor intensity referencing compares the odor in the ambient air to the odor intensity of a series of concentrations of a reference odorant. A common reference odorant is n-butanol.

Odor intensity can be expressed using an odor intensity scale, which is a verbal description of an odor sensation to which a numerical value is assigned. Odor intensity can be divided into the following categories according to intensity:

0 - no odor

1 - very weak (odor threshold)

2 - weak

3 - distinct

4 - strong

5 - very strong

6 - intolerable

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