In the military sense, obsolete as of year of 2011 - Serbia now has mercenary army, US style.
The movement of air caused by open windows and/or doors is, traditionally, one of the greatest fears of Serbs. Catching cold from a draft is something your parents keep you from. Even Vuk Karadžić, almost 200 years ago, wrote about it.
While it's possible to catch a cold by being exposed to a draft if you're all sweaty (and the clime is not so humid, so it does evaporate rapidly), the dangers of draft are exaggerated by default. The typical scene has people in a vehicle, under the sunshine, enduring swelter until the vehicle finally starts moving. Then the aerial refreshment starts coming through the windows - the upper fourth of every other window on a bus can slide halfway, plus there's a hatch or two on the roof - and within a minute someone will close it. Then someone else will open it again. There may be harsh words exchanged, but generally the oponents of the draft win.
Nowadays most of the inter-city buses have air conditioning, but city buses and trains mostly don't, which prevents the whole scene. OTOH, it does create a different scene sometimes, if someone did catch a cold in the home of some nouveau riche, who keeps his house temperature lower than in winter, while it's 36o outside. As the proverb goes, "whom snake bit, fears even lizards", so these would complain against AC being in any use.
Another common thing is "do not sit on cold stone/concrete/bricks".