Breathing pure O
2 in space applications, such as in some modern space suits, or in early spacecraft such as Apollo, causes no damage due to the low total pressures used. In the case of spacesuits, the O
2 partial pressure in the breathing gas is, in general, about 30 kPa (1.4 times normal), and the resulting O
2 partial pressure in the astronaut's arterial blood is only marginally more than normal sea-level O
2 partial pressure (for more information on this, see space suit and arterial blood gas).
Why is breathing oxygen in space craft not dangerous to health? What is the oxygen partial pressure of space suits? How much of normal is the oxygen breathed in space suits? How much damage does breathing oxygen in space conditions cause? What si the comparison to sea level with the oxygen level in space suits?