Odours are generally caused by organic molecules in the gaseous phase. They comprise certain elements in specific combinations which are detectable by the sense of smell.

Unpleasant odours are usually derived from unsaturated organic compounds, such as are formed when vegetable or animal material decomposes. These odours frequently arise from compounds containing carbon/nitrogen and carbon/sulphur bonds, and generally indicate that decomposition is taking place in an insufficiency of oxygen.

Naturally occurring unpleasant odours frequently indicate the presence of one or more of the following groups of compounds:

Odour sources include faecal matter, urine, decomposing flesh, blood, food waste and dirty water. These are typically found in sewage treatment plants, landfills, animal cages, hospitals and public urinals etc.

Unpleasant odours can cause poor appetites, lowered water consumption, impaired respiration, nausea, vomiting, watering eyes. Odours at low concentration can cause psychological stress, public fears for safety, or be a barrier to total public acceptance or increased patronage, some odours at high concentration may cause harm.

Continuing odours can lead to deterioration in staff morale, personal and community pride, human relationships, discourage capital investment and lower socio-economic status. Severe problems can result in decline in market and rental property values, tax revenues, pay rolls and sales.

Odour control practices in the past have consisted mainly of venting airbourne odours to atmosphere, or masking them with a reodorant.

Biotechnology in odour control involves accelerating the rate of biological decomposition using natural processes, and providing sufficient oxygen for complete oxidation of the odiferous substances.

Certain naturally occurring bacteria are effective in providing oxygen for aerobic decomposition and are capable of removing odours from decomposing organic material in a matter of hours. They also assist in the complete decomposition and oxidation of all organic substances, typically achieving these results in 7-21 days.

In severe cases of oxygen depletion, specially cultured aerobic bacteria can be introduced, together with the nutrients they require for rapid reproduction.