Actually, the smell/gas detection can be accurately performed using gas chromatography (GC). However, it is expensive, bulky, and need special skills to operate. The alternative is electronic nose (e-nose) utilization. It cheaper, smaller, and easier to operate than GC but there are several challenges:

1. Existence of noise in gas sensor.

Gas sensor noise can be divided into two sources i.e. internal and external noise. Internal noise is caused by semiconductor noise and unstable power and external noise is caused by ambient conditions such as humidity, temperature, etc. The sample article which discuss to deal with noise in gas sensor as follows:www.sciencedirect.com/science/article/pii/S0169743916304907

2. The huge overlapping selectivity of sensor combination in the gas sensor array. The particular application can has different combination of gas sensor. Hence, the sensor array optimization is necessary. The following article is a sample approach to deal with this issue: www.praiseworthyprize.org/jsm/index.php?journal=irecos&page=article&op=view&path%5B%5D=19107

The example of gas concentration analysis using e-nose is demonstrated by this article ieeexplore.ieee.org/document/7886744/