Odour threshold is the lowest concentration of a substance in air that can be smelled. Odour thresholds are highly variable because of the differing ability of individuals to detect odours.

n-butanol is used as a standard odorous gas in odour measurement by using dynamic olfactometer (AS/NZS 4323.3:2001; CEN EN 13725:2003). In these standards, the detection odour threshold is described as 40 ppb.

1 OU/m³ (odour unit) is defined at that concentration of an odour in an air sample that can be perceived by 50% of the observers. One OU/m³ equals the odour perception of 40 ppb n-butanol according to the CEN standard.

The statistic value of odour threshold values of n-butanol may reflect the accuracy of the measurements of a laboratory. Our most recently measured odour thresholds of n-butanol are shown in the following figure.