Final answer:
Lack of air is both a necessary and sufficient condition for human death because human cells require oxygen for energy production, and without it, critical body systems fail.
Step-by-step explanation:
Lack of air, specifically oxygen, is a both necessary and sufficient condition for human death. Without oxygen, humans can survive for only a few minutes. This is because our body's cells require oxygen for respiration, which is the process of converting glucose into energy. Without sufficient oxygen, cells cannot produce the energy they need to function, leading to the failure of critical organ systems and ultimately death.
Also, the human body reacts to low oxygen levels by increasing the breathing rate to obtain more oxygen or attempting to eliminate excess carbon dioxide, which if accumulated can lead to a condition called hypercapnia. High carbon dioxide levels are actually more detectable by the body than low oxygen levels and will trigger the urge to breathe more than low oxygen levels alone. Nonetheless, the crucial factor resulting in death when the body lacks air is the absence of oxygen.