http://en.wikipedia.org/wiki/Cocoanut_Grove_fire
As is common in panic situations, many patrons attempted to exit through the main entrance, the same way they had come in. However, the building's main entrance was a single revolving door, immediately rendered useless as the panicked crowd scrambled for safety. Bodies piled up behind both sides of the revolving door, jamming it to the extent that firefighters had to dismantle it in order to get inside. Other avenues of escape were similarly useless: side doors had been bolted shut to prevent people from leaving without paying their bills. A plate glass window, which could have been smashed for escape, was instead boarded up and unusable as an emergency exit. Other unlocked doors, like the ones in the Broadway Lounge, opened inwards, rendering them useless against the crush of people trying to escape. Bartender Daniel Weiss and entertainer Goody Goodelle both survived in the Melody Lounge; by dousing a cloth napkin with a pitcher of water and breathing through it, Weiss was able to escape by crawling through the kitchen and other subfloor areas, while Goodelle and several other employees were able to escape by crawling through a barred window in the kitchen. Five survived by taking refuge in a walk-in refrigerator. Fire officials later testified that, had the doors swung outwards, at least 300 lives could have been spared. Many young soldiers perished in the disaster, as well as a married couple whose wedding had taken place earlier that day.
And that, boys and girls, is why we have building codes.
(It's also why many professional engineers in the US and Canada take an oath, like doctors. Proper engineering is a serious business. Lives are at stake.)