1st riddle is Nothing?
2nd is being buried alive? This because you're being drowned of oxygen and since it is soil, you most likely are not wet. However soil is always moist which means it is incorrect; therefore you need a different alternative to soil for the answer. That I cannot think of.
Riddle:
A man decides to quit his job, so he turns off the lights, and walks out of the room; 200 people die. Why do 200 people die?