Reaffirmed 2022

1. Scope

This standard prescribes a consistent series method for the determination of threshold odour. This method is applicable to all types of water and waste water

2. References

The sample of water is diluted with odour-free water until a dilution of least definitely perceptible odour to each tester is found. The resulting ratio by which the sample has been diluted is called the threshold odour number (T.O.). As odour sensitivity differs with individuals and same person may also not be consistent, a panel of not less than five persons and preferably ten persons or more is recommended. As an absolute minimum two persons are necessary; one to make sample dilutions and other to determine threshold odour.

The following conditions should be considered while selecting panel members:

a) panel members shall not be suffering from any ailments that affect their perception of smell, such as cold, fever, sinusitis etc.

b) panel members should not engage in smoking, drinking (except water), and chewing gums/ sweet from 30 minutes before and during the testing.

c) panel members should avoid substances that can cause interference to smell, for example, perfumes, deodorants, cosmetics etc.