Real-time Odor Tracking VS olfactometry
Olfactometry is a great tool to translate into a quantitative and objective value the complexity of odor perception (see blog: Are odors additives in terms of the intensity?)
Dynamic dilution olfactometer
However, in some circumstances, real-time values are required to provide the dimension of odor fluctuations of a process that olfactometry can hardly provide. Indeed, olfactometric measurements require sampling and lab analysis that practically or financially limit the amount of values available to understand the odor fluctuations out of an odor source.
Let's take the example of a biofilter exit treating composting odors. In this case, the process generates pulsed air flow for windrow forced aeration.
What do we see here?
First, using today’s standard ‘manual’ odor sampling and measurement method (blue dots), we measure three separate odor concentrations at different points in time, then connect the dots to obtain rectilinear segments.
In this case, looking at a biofilter designed to limit odor output to 400 odor units, the ‘manual’ method (olfactometry) would indicate that the biofilter is working fine and the neighbors would perceive no odor. However, there are still odor complaints; no one knows why.
Then we install an electronic nose OdoWatch (magenta curve); this gives us continuous measurement; and we now see that there are odor peaks up to 750 odor units.
The mystery is solved. Now we can act to deal with the problem. Measuring daily average odor concentration may doesn’t work. The human nose senses peak values not average values. Thus the monitoring system needs to measure odor concentration at very short intervals. OdoWatch measures odors every second.