Assessment of detection thresholds of metal oxide sensors based e-nose to the pollution emitted by odorous sources.

The paper describes a method to assess the global concentration level of a complex odorous gas mixture which is detected by an electronic nose, and consequently to assess the detection threshold of the instrument for that particular odour. The studied case is the odour generated by urban waste composting facilities. The measurement is performed in the lab with an array of 12 tin oxide gas sensors on samples collected near the emission.
The selected method consists in finding an equivalence between the response of each individual sensor to the concentrations of ethanol used as a standard gas and the responses to various dilution of the original sample.
The main issues of that procedure are the order of magnitude of the "concentration" of the non-diluted compost emission sample expressed in ethanol-equivalent and the detection threshold of the sensor array for the compost gas.
The latter result requires a suitable definition of the detection threshold, based on the signal to noise ratio.
The conclusion is that the detection threshold of Tagushi sensors, expressed in equivalent-ethanol, is generally lower than 1 ppmv and is just slightly higher than the perception threshold of the human nose for the odour gener-ated by compost.