Strange odors ... locating and eliminating

[Kenneth LaVoie]

We have 3-4 units out of 48 that have "mystery odors" -- We have had no luck in getting rid of them or pintpointing their location. they've VERY old buildings but there's no carpeting so once we do, we SHOULD be able to kill them. My cleaning man & maintenance man BOTH cannot detect any unpleasant odors in these places, but they're there. My wife, me, and every prospect has detected them like a 2x4 between the eyes.

They smell like dirty laundry, maybe...possibly a hint of urine, but mostly like unwashed socks, underwear and armpit smell, I can go on and on ... 

Has anyone had a problem like this? Any tips on ID'ing and correcting the odors? Is there a "nuclear" option like those Ozone machines, or some nerve gas level material I can bomb the place with!!

Thanks so much for any hints.