What is air quality?

What is air quality? Air quality deals with the composition of air and the suitability of air for a certain application.

What are the factors that determine air quality?

The air we breathe has a very complex composition and it contains over one thousand different compounds. The main elements found in air are nitrogen, oxygen and hydrogen. Without these compounds, life on earth would be impossible.
Air quality is determined by the composition of air. The presence or absence of various substances and their concentrations are the main determining factors for air quality. Consequentially, air quality is expressed as a concentration or intensity of contaminants, as presence of (micro)organisms, or as physical appearance. Examples of contaminants that are an important indicators for air quality are sulphur dioxide and dust and grime particles. Physical appearance of air can be measured, for instance by determining air turbidity.

Who determines the policies for air quality?

Air quality is a subject on the programme of many international authorities these days. One of the organisations concerned with air quality is the World Health Organisation (WHO), which recommends standards for air contaminants that can cause health effects.
The United Nations deal with the subject of air quality in Agenda 21 and the Economic Committee of Europe has been working on a series of international protocols.
Each government has its own standards for air contaminants. These standards are maximum concentrations, which may be present in air. The standards may vary greatly between various countries. Governments of different countries, for example in the European Union, are trying to suit their policies for air contamination standards.

What is stench?

One of the ways in which we are confronted with air pollution is by smelling it. When we can detect a substance by scent, this substance possesses a distinctive smell. When the detection of a substance is experienced as unpleasant, we call this stench. Stench does not necessarily mean that the air is polluted with damaging contaminants, but it does cause nuisance.
Smell nuisance is not easily determined, because each person experiences smell in a different way. To measure smell levels we use a human nose and an air thinner device (olfactometer)