By definition, what they are telling you to do is to pull that alarm upon reading the sign. Don't hesitate...pull it now in case there is a fire! What they mean to say of course is "Pull in the event of a fire" but for whatever reason that message is reworded. So there it is. General ignorance leads us to not question errors written on almost every fire system and elevator in the land.
Cheers to general ignorance! Now let's not get me started on those 12 items or less (Fewer!) signs!