The U.S. Defense Advanced Research Projects Agency (DARPA) launched the "Odortype Detection Program" in 2002. It had two goals:
The goal of Phase 1 will be to determine whether an exploitable, robust signature corresponding to individual human odortype exists...
The goal of Phase 2 will be to build a detector that can reliably detect the signature identified in phase 1 with high sensitivity and specificity.
By 2007, DARPA had changed the name of the program to the "Unique Signature Detection Program," but its goals remained essentially the same
to determine, by means of a well-developed scientific methodology, whether there are unique signatures in emanations that can be used to identify and distinguish specific high-level-of-interest individuals within groups of enemy troops or combatants, and if so, to develop enabling technology for detecting and identifying those specific signatures. The program consists of an interdisciplinary team of performers using state-of-the-art techniques to evaluate the statistical, biological and chemical nature of individual emanations. Once the nature of the chemosignal has been characterized, performers will determine the impact of non-genetic factors (e.g., diet, stress, health, age) on the signal in order to determine whether the signal can be robustly extracted from a complex and varied chemical background. If an exploitable robust signature is identified, the program will then pursue detector development.
I haven't been able to find out what's become of the program since 2007. Though I'd wager that the U.S. government hasn't completely abandoned the idea since being able to identify people by their smell would be a hard-to-defeat surveillance technology. (Assuming that we all really do have a unique 'odortype' that can't be camouflaged with fragrance or by eating stinky food).
However, I did find a report on the program from 2005
that included the interesting detail that they field-tested the technology on seven sets of twins at Williamsburg, VA and Research Triangle Park, NC:
a field study was planned and conducted by RTI. In this study, identical twins and a family member (sibling or parent) were recruited. Each group went to either Williamsburg, VA, or Research Triangle Park, NC, for a four-day stay at a hotel. During this stay, daily sweat samples were collected onto polydimethylsiloxane membranes, as described in earlier reports to DARPA/ARO. A total of seven sets of twins were recruited. The goal was 30 twin pairs. Given the relatively poor response rate and the need for project resources to adequately address the data processing and statistical analysis needs of the overall USD program, the field study was terminated.