Same purpose it serves in newer buildings above a door or just in a wall, ventilation. Hot air collects at the ceiling so a window or other opening up there lets it out. When used over a door it's so ya get the ventilation without having to open the door. Of course in older office buildings with a Chinese restaraunt on the ground floor,it's so the hard boiled detective's office has nifty film noir shadows and so he can hear conversations between the classy dame with legs that didn't quit who just left his office and the slimy little gunsel, with the bulge under the arm of his ill fitting jacket with checks so loud it affects the private dick's hangover like a load of bricks landing on a loaf of day old bread, who is about to burst in. That gives him time to think of pithy phrases with which to crack wise . In response to Hungry Guy's question ( and for Andersen)[may 14, 05] I gave the guy sitting in the one client's chair that didn't wobble an up and down and thought longingly of the shot of rye in the bottle I kept in the one drawer that actually pulled out of the desk. At least I thought there was still a shot left. If I was smart I give this guy the bums rush and then at least smell the cork. But there was something hinky about this guy, then it hit me. The guy was hungry, hungry for answers just like all the other people who sat in that chair. Well, the sign on the door and the 3rd floor window, the one that had been painted shut in the Coolidge administration, behind me had my name on it and finding answers was my business, sure sometimes it was a dirty business, but then it was a dirty office, with a dirty door and a dirty window, if I could get a retainer from this guy, maybe I could hire a cleaning lady. I gave myself a pat down lookin for a match to light a smoke and said, "OK, mac, I'll put ya wise and this is the straight lay. It ain't gotta be over a window , see? It can be on any wall. And it ain't gotta be glass either and it don't gotta be hinged like a transom., it can be a sliding panel gizmo of wood. Ya driftin' with my flow?" The guys face was as blank as my bank book. " And it works even better if ya got a similar arrangement on an opposite wall down low so cooler air can come in, like down by the floor, even in the floor over a cool basement. That way ya get a cross ventilation. " I'd found a match but the cigarette package I pulled out of my pocket was as empty as the guys expression. "It works even better if the temperature outside is cooler than inside and you can vent that in and vent the hotter air to the outside. Got it?" He didn't say a word. " What's with the Chaplin act, bud? Ya got your answer, now fork over the cabbage." "I'm terribly sorry," he said, standing up, "I merely came in to ask if you knew when the Chinese restaurant on the ground floor opens." He ankled out of the office before my mind could shift gears. It wasn't answers he was hungry for after all, just moo goo gai pan, I mused as I leaned back in the creaky desk chair and stared at the dirty transom over the dirty door. I remembered why the chair creaked when it kept tilting back and dumped me through the dirty window and onto the dirty pavement below. It was peaceful there, lying among the diamonds of shattered glass looking up at the snowflakes floating across the sky, big multi- colored snowflakes. It wasn't snowflakes at all it was the papers blowing off my desk and out the window like confetti at Guy Lombardo's funeral. Then there were two dirty grimy faces staring down at me staring up. It was two of the hop heads that shacked in the alley. "Who is it?" the tall one asked. " I think it's that ex-flatfoot with the office on the third floor," the taller one answered. "Flatfoot? He's flat all over now!" " Yeah, but look up there at all the papers blowing out, he really had nice ventilation up there. He musta left the transom over the door open." "They don't gotta be over a door ya know." I could have told them if the transom was open, I coulda told um if it was over the door. But I didn't, I didn't tell um anything. I wouldn't be telling anybody anything anymore. Maybe I was finally going to a place where my questions would be answered. But probably not. I was gonna wind up in a place where there was no circulation and the air was hot, no matter how many transoms were open.

Besides hot air, it also lets out smoke that collects near the ceiling, or it did in the old days when rooms were heated by fireplaces and woodstoves. Yes, I know , this is ventilation, too. But I thought I would make the point that ventilation isn't only about hot air.