A joke to illuminate the answer:
A physicist and engineer were roommates in college. One night a fire broke out in their apartment. The engineer woke up first and saw the fire. He remembered the fire extinguisher in every unit, grabbed it and pulled the pin, as instructed, and sprayed the fire with the sodium bicarbonate contained within.
Incredibly, the next night, the exact same fire sprung up in their apartment. The physicist was the first to wake up this time. He saw the fire, saw the fire extinguisher, then went back to bed happy knowing there was a solution to the problem.
