Another aspect that should be considered as part of the quality of indoor air is its smell, because smell is often the parameter that ends up being the defining factor.The combination of a certain smell with the slight irritating effect of a compound in indoor air can lead us to define its quality as fresh and clean or as stale and polluted.
They have been obtained by measuring adverse effects on health resulting from exposure to contaminants in the environment.
These standards are therefore useful as general guidelines for an acceptable quality of indoor air, as is the case with those proposed by the World Health Organization.
Smell is therefore very important when defining the quality of indoor air.
While odours objectively depend on the presence of compounds in quantities above their olfactory thresholds, they are very often evaluated from a strictly subjective point of view.
It should also be kept in mind that the perception of an odour may result from the smells of many different compounds and that temperature and humidity may also affect its characteristics.
From the standpoint of perception there are four characteristics that allow us to define and measure odours: intensity, quality, tolerability and threshold.
The connection between the use of a building either as a workplace or as a dwelling and the appearance, in certain cases, of discomfort and symptoms that may be the very definition of an illness is a fact that can no longer be disputed.
The main culprit is contamination of various kinds within the building, and this contamination is usually referred to as poor quality of indoor air.
In addition, for many contaminants present in the air, the effects of acute exposure are well known, whereas there are considerable gaps in the data regarding both long-term exposures at low concentrations and mixtures of different contaminants.
The concepts of no-effect-level (NOEL), harmful effect and tolerable effect, already confusing even in the sphere of industrial toxicology, are here even more difficult to define.
When considering indoor air, however, it is very difficult to measure odours from a chemical standpoint.