McCarran smells like an old dusty building that has black mold growing in some gross corner. You can immediately smell the must coming in, but if you're there long enough you sort of forget until you go outside. It also smells like metal and mildew, and occasionally the sweat of troops who haven't found the time to shower yet, because AC hasn't been working for a few centuries. Just smells like industrial barracks
Colonel Hsu's office isn't much better, but at least he tries to hide the smell with some expensive pre-war cologne he found years back, which he also drowns himself in if he hadn’t found the time to shower that morning either. Sometimes his office smells like ink after a pen explodes, or coffee if he's working late hours. Not good coffee though. Cheap, watered down stale coffee.
Boyd's office is a similar story, but no cologne or perfume in sight. Instead, you can smell the electronic components of CRTVs heating up in her office. Moisture on the walls cause mold and the plaster to fall off, but she pays no mind to the smell. Regardless, she prefers to keep her office doors open.
There's a unique sharp smell of metal in Curtis' office due to amount of filing cabinets he has in there. Moisture from the air and his hands cling to the cabinets, so the entire room smells like steel. Not to mention all of the equipment he needs for the attack on the monorail. Given his room is in a tucked away place next to the bathrooms, regular leakage leads to a little extra mold growing behind the plaster. If anything that is what causes his insomnia since he's sleeping right next to it.
It's similar in Concourse, if anything the scent of BO is even stronger with all the troops hanging around. Occasionally you'd get a whiff of Farber's cooking, which could be a good thing or a bad thing. If you're lucky, you may even smell bleach from someone scrubbing the floors, or maybe even spilled Nuka Cola.