You can distinguish chemicals by their smell

Odor offensive substances


Work techniques

The use of substances that are highly annoying in the communal laboratory due to their smell and that smell penetrating even in the smallest concentrations should, if possible, take place in a separate workplace. Even if they are not necessarily harmful to health or even toxic, the experiments should be carried out using techniques such as those used for highly toxic substances.

Recognize odorous substances

All odorous substances are

  • highly volatile or fine dust; so if they are released they can get to the nasal mucous membranes,
  • sufficiently soluble in water; so they can penetrate the watery environment of the nasal mucous membrane and reach the olfactory receptors,
  • sufficiently fat-soluble; so they can penetrate the membranes of the olfactory cells.

Many aliphatic, aromatic or halogenated hydrocarbons, as well as compounds containing oxygen, sulfur and nitrogen, have the basic properties mentioned. Some inorganic chemicals are also among the odor-intensive substances, such as hydrogen sulfide and ammonia.

The smell of a substance cannot be recognized by its chemical structure. Structurally different compounds can trigger an almost identical odor sensation, on the other hand structurally similar substances have a very different odor.

Odor-intensive chemicals

If an odor is noticeably perceived, the odor threshold (perception threshold) has been reached. The concentration at which it is recognized is called the recognition threshold. It is usually 2-3 times above the perception threshold. Information about the odor or detection threshold of odor-intensive substances should generally be looked up in the safety data sheets or in the relevant substance information. The comparison with the respective occupational exposure limit makes it clear whether the odor-producing substance is perceived at a concentration that is harmless to humans, i.e. whether the odor has a warning effect. Often, however, the detection threshold is also significantly lower.

The best-known example is hydrogen sulfide: You can smell it in very low concentrations far below the occupational exposure limit. But be careful! Odor substances are not perceived equally by all people. About 10% of the population should not be able to smell hydrogen sulfide! And substances cannot be recognized by their smell in all concentration ranges: hydrogen sulphide, for example, is odorless in the range of its deadly concentration due to paralysis of the olfactory nerves!

The intensity with which an odor is perceived generally increases with increasing concentration, but not linearly. In addition, the sense of smell adapts: With prolonged exposure, the perception of strength of smell decreases again.