Emergency exits - how they should be?

Recently, I attended a seminar and found the two doors marked as EXIT inside in the conference room, are leading to the same corridor. The conference room is located somewhat deep inside the building. I thought it is dangerous as any fire in the corridor will trap the seminar room occupants. Then during lunch time, I went behind the screens used for display of presentations and found two doors leading to outside of the building. Though, these doors are not marked as EXIT, still they serve the purpose. However, as they are not visible and there are no directional marks, people may or may not use them in an emergency.

Some of the guiding principles for emergency exits are,

1. doors should open outward
2. there should be one emergency exit for every 75 ft distance
3. emergency lighting along the corridor to maintain minimum illumination in case of failure of regular power supply
4. self glowing display signs (EXIT, arrow marking, etc)
5. availability of keys near the doors marked emergency exit, with hammer to break the box containing keys
6. not blocking the emergency exits
7. not having stairs in front of emergency exit doors

At some places, it looks funny to see signs of EXIT and directional arrows exactly on the doors instead of direction marks along the wall from inner rooms to outdoors.