[logfromblammo]

As far as I am aware, the smallest available odor sensor is a trained bee or wasp. The hymenopterans are classically conditioned to extend their tongues when exposed to a particular chemical or odor profile. Then they are restrained inside a plastic cartridge, such that whenever they extend their tongues, a tiny button is pressed.

The cartridge is then loaded into a handheld device that lights an LED whenever the insect detects the odor.

Much cheaper than trained dogs, and the purely electronic detectors are not quite as robust [yet]. The downside is that you can't exactly buy it once and keep using it for the next 10 years.

Sniffer insects have been used to detect bombs, fungal blight, cancer, diabetes, pregnancy, contraband drugs, and uranium.

[throwanem]

I thought this was all a joke, but apparently only some of it is: https://en.m.wikipedia.org/wiki/Hymenoptera_training

[logfromblammo]

The cartridges are not mentioned in that article. I saw them on a television program. They so strongly resembled rows of schoolchildren sitting at their desks, that I half expected a bell to ring before the bees put their textbooks away and go on to learn another scent.

The commercial product is the VASOR136 by Inscentinel Ltd.

https://www.sheffield.ac.uk/polopoly_fs/1.269373!/file/Sniff...