What is the minimum air oxygen level to sustain human life? I think air has about 20% oxygen.

>What is the minimum air oxygen level to sustain human life? I think air has about 20% oxygen.

related…

https://en.wikipedia.org/wiki/Life_support_system

A crewmember of typical size requires approximately 5 kg or 11.0231 lb(total) of food, water, and oxygen per day to perform the standard activities on a space mission, and outputs a similar amount in the form of waste solids, waste liquids, and carbon dioxide. The mass breakdown of these metabolic parameters is as follows: 0.84 kg of oxygen, 0.62 kg of food, and 3.52 kg of water consumed, converted through the body’s physiological processes to 0.11 kg of solid wastes, 3.87 kg of liquid wastes, and 1.00 kg of carbon dioxide produced. These levels can vary due to activity level, specific to mission assignment, but will correlate to the principles of mass balance. Actual water use during space missions is typically double the specified values mainly due to non-biological use (i.e. personal cleanliness). Additionally, the volume and variety of waste products varies with mission duration to include hair, finger nails, skin flaking, and other biological wastes in missions exceeding one week in length. Other environmental considerations such as radiation, gravity, noise, vibration, and lighting also factor into human physiological response in space, though not with the more immediate effect that the metabolic parameters have…

….Space life support systems maintain atmospheres composed, at a minimum, of oxygen, water vapor and carbon dioxide. The partial pressure of each component gas adds to the overall barometric pressure.

By reducing or omitting diluents (constituents other than oxygen, e.g., nitrogen and argon) the total pressure can be lowered to a minimum of 21 kPa, the partial pressure of oxygen in the Earth’s atmosphere at sea level. This can lighten spacecraft structures, reduce leaks and simplify the life support system.

However, the elimination of diluent gases substantially increases fire risks, especially in ground operations when for structural reasons the total cabin pressure must exceed the external atmospheric pressure; see Apollo 1. Furthermore, oxygen toxicity becomes a factor at high oxygen concentrations. For this reason, most modern crewed spacecraft use conventional air (nitrogen/oxygen) atmospheres and use pure oxygen only in pressure suits during extravehicular activity where acceptable suit flexibility mandates the lowest inflation pressure possible.

https://en.wikipedia.org/wiki/Breathing_gas

bob(from black rock) said:

What is the minimum air oxygen level to sustain human life?

0%

Ref: The Crawling Hand

Movie masterpiece from 1963

Ian said:

bob(from black rock) said:

What is the minimum air oxygen level to sustain human life?

0%

Ref: The Crawling Hand

Movie masterpiece from 1963

That would sustain us for as long as we deserve to be sustained.

Wiki says..

Serious hypoxemia occurs (1) when the partial pressure of oxygen in blood is less than 60 mm Hg, (the beginning of the steep portion of the oxygen–haemoglobin dissociation curve, where a small decrease in the partial pressure of oxygen results in a large decrease in the oxygen content of the blood); or (2) when hemoglobin oxygen saturation is less than 90%. Severe hypoxia can lead to respiratory failure.

——-

You can go a lot lower than 90% if it is short lived or else you’ll be short lived.

http://www.thenakedscientists.com/forum/index.php?topic=44734.0

bob(from black rock) said:

What is the minimum air oxygen level to sustain human life? I think air has about 20% oxygen.

This question was asked only a month or so on this forum, and I gave a thorough detailed answer.

I can’t be bothered going through all that again, but note that some climbers have climbed Mt Everest without oxygen. That’s the equivalent oxygen partial pressure of a whisker under 7%.

mollwollfumble said:

bob(from black rock) said:

What is the minimum air oxygen level to sustain human life? I think air has about 20% oxygen.

This question was asked only a month or so on this forum, and I gave a thorough detailed answer.

I can’t be bothered going through all that again, but note that some climbers have climbed Mt Everest without oxygen. That’s the equivalent oxygen partial pressure of a whisker under 7%.

One of them was my old boss, LtCol Cullinan.