Odors are chemicals in the air that can interact with olfactory receptors. Unfortunately, human noses and olfactory receptors are relatively poor chemical detectors compared to many other organisms. For this reason, humans have trained companion animals that can communicate with us to detect important odors. Pigs are used by mushroom hunters to detect the odor of truffles. Dogs can be trained to detect a variety of odors including drugs, explosives and even insect infestations such as bed bugs and termites.
Some insects are very good at detecting a variety of odors. How can they communicate with us? Through technology of course. Wasps can be trained to respond to chemicals by feeding them sugar water at the same time they can smell the chemical of interests. After several bouts of feeding with odor present, the wasps will associate the chemical odor with the food and respond to the chemical odor- sort of a wasp version of Pavlov’s dogs.
The wasps can be placed in a tube and air drawn into the tube with a fan. If the air contains the odor of interest, the wasps will crowd around the air intake. Sensors around the air intake can alert the user.
Although this technology works, it is necessary to keep a colony of wasps and constantly train new ones as the old ones die. For this reason, attention is turning to the antennal receptors themselves in hopes of producing an artificial antenna that is as sensitive to important odors as a wasp.
Wasp Antennae
Living With Insects Blog 
I was just curious as to what kinds of chemicals they are using the wasps to look for and why?
They are using all kinds of chemicals that would allow detection. Land mines give off chemical odors. Bombs give off chemical odors. So there are military clean up and security uses. Bed bugs are hard to detect, but give off odors. Termites can be difficult to detect. So wasps can be trained to any of those odors.
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