Emergency!

The boss who was on the 25th floor of the building called up the clerk on the ground floor for an important file.
Since it was rather urgent the boss told the clerk it was an emergency and that he should hurry with the file.
After more than 30 minutes the clerk appears all tired and panting for breath.
The Boss asks him why he was panting and what caused the huge delay.
The clerk replies, 'Boss when I went to the lift it said' during an emergency please use the staircase'!!!