The aim of field inspections is to register the odours immediately recognized under real field conditions.
The main idea of field inspections is to estimate the degree of annoyance in a determined problematic area by means of the olfactory capacities of a group of people (or panel) specially trained and "calibrated" for this purpose. To this effect, the study area is divided in smaller assessment squares and the people of the panel is sent to the nodes of this squares at different times of the day and in a determined order to allow the most diverse conditions. Anytime a person of the panel reach a node, smells the air and take notes of odour parameters (Intensity, hedonic tone, etc.), weather conditions and some other data on site.
For the purpose of taking notes about the field conditions, a normalized form is widely used. In this form different parameters are registered, such as the quality of odours, hedonic tone, wind direction, etc.
Another interesting way of recording odour data is by means of a hand held device powered with a database linked to a GPS system. Often it is found that the odour panellist is in his/her house filling the forms instead of in the monitoring point. Another solution to this common problem is to have some inspectors on the area.
Field inspections have several advantages when compared with other methods in cases where there are many sources of odour emission or when the sources of odours are not well defined.
Field inspections according with the VDI/DIN 3940 (German method)
In Germany, the main criteria is obtained from field inspections and evaluation of the exposition to odours. This method normally uses a panel of 12-20 people and a year of annotations (a period of 6 months is also allowed). The main drawback of this method is its cost, as both time and amount of people involved, raise the final cost of the odour measurement.
Back-wind field measures with a panel (Belgium method )
In Belgium, a combination of techniques is being introduced in a normative iniciative of the flemish government, aplying techniques of field inspection using a panel to obtain estimations of the emissions, combined with dispersion modelling. Carried out on site, it is normally performed 12 times in 3 different days to estimate the emission rate of the sources, through an inverse dispersion model. This method is in many cases lest costly than the former.
An interesting link is here.