communicate communication danger emergency emergency exit escape exit fire fire escape hazard safety sign warning clear keep metal text dangerous directing direction directions exiting green guide help icon indoor instruction leaving life logo man path pictogram protection run running save signs symbol urgency wall jump parachute doors fire door keep clear no obstruction security arrow door doorway architecture elements England english external Great Britain spiral stairs steps white construction corkscrew stairs escape route escape way fire exit flight of winding stairs grate grated helical shape shapes spiral stair spiral staircase stair staircase wentletrap