The key to this riddle is realizing that you do not have to pull the emergency switch in the first room, the entrance, and so that room will not lock down. You can leave it, and then return to it and go out the other door. And indeed this is exactly what you need to do so you can hit all 16 rooms and end in the exit room.
Once you know to leave and reenter the first room, there are eight possible solutions to travel through all the rooms and end at the exit. Because the first room is clear, you can backtrack through it to get back on the right track and pull the emergency switch in every room, saving the world from agonizing death by ancient virus.
It can't be seen, can't be felt, can't be heard and can't be smelt. It lies behind stars and under hills, and empty holes it fills. It comes first and follows after, ends life and kills laughter. What is it?
If you pile up coins one on top of another until they get as high as the Empire State Building - would you be able to fit them all into one average sized room?
(The 'Google Riddles' are interview questions those who wish to get hired were asked).
Yes, you could.
How do we know this? If the Empire State Building is about 100 levels tall, and each level is about an average room in height, that means we can divide the giant pile into 100 piles of one level each. Would 100 piles of coins fit in a room? Of course it will, with lots of room for more.