Humans can survive at a wide range of atmospheric pressures, but there are limits to how high or low these pressures can go without causing harm. Generally, the normal atmospheric pressure at sea level is about 101.3 kPa (kilopascals) or 1 atmosphere (atm).
At high altitudes, atmospheric pressure decreases. Humans can acclimate to lower pressures, and many people have successfully ascended to altitudes over 8,000 meters (about 26,247 feet), although supplemental oxygen is often necessary above 7,500 meters due to the reduced availability of oxygen. Permanent exposure to pressures lower than those found at sea level can lead to altitude sickness, which can be life-threatening.
On the other hand, at pressures significantly higher than sea level (like those experienced during deep-sea diving), humans must also take precautions. Pressures above approximately 3 atm can make breathing normal air hazardous due to increased nitrogen absorption, which can lead to nitrogen narcosis. Moreover, at depths of around 10 atm or more, the risk of oxygen toxicity increases significantly.
In summary, while humans can survive within a range of atmospheric pressures, typically between about 0.2 atm (near the limit of survival) to around 3 atm (with proper breathing gas and precautions), going outside these ranges can lead to serious health issues.