Warwick University's e-nose technology has been around for quite a while: https://warwick.ac.uk/fac/sci/eng/research/impact/electronicnose/

As far as I understand their technology, they sample gas, and analyse it using a solid state CMOS device to generate a signature signal for particular compounds/mixtures.  The devices have been used in a variety of industrial gas sensing applications.

There has been some progress in using e-noses in medical diagnosis, for instance this paper reports the use of e-noses to sample volatile organic compounds from urine in type 2 diabetes diagnosis: https://www.ncbi.nlm.nih.gov/pubmed/30513787