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Suppose my character doesn't wear any kind of protection and is an average human being and the transitions from normal atmosphere to vacuum and back are instant.

Further suppose that my character receives immediate medical attention (with present day technology and knowledge) from a medical professional after the incident.

What is the maximum amount of time my character can spend in the vacuum of time before they can't be saved anymore?

Note that this question isn't about what would happen to my character, but how long is survivable. So a question asking what would happen to a body if it was exposed to the vacuum for 9 seconds doesn't answer my question.

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  • $\begingroup$ @Radovan Garabík No not really since the question already specifies a time, but I want to know the maximum amount of time while still surviving. $\endgroup$
    – Cookie04
    Apr 22 at 9:14
  • $\begingroup$ The point of the duplicate votes is not that the question is the same, but that the answers appear to satisfy all conditions of your question. If that's not the case then please edit your question to clearly explain what's missing. $\endgroup$ Apr 22 at 11:26
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Death in vacuum occurs within seconds or minutes.

The main causes seem to be asphyxiation (and resulting damage) and trauma from pressure differences (ruptured blood vessels and lungs). A quick Google search suggests that you would lose consciousness in around 15 seconds with death occurring shortly after. It's not a good idea to hold your breath as full lungs will rupture.

This article mentions some experiments with animals:

But death is not instantaneous. For example, one 1965 study by researchers at the Brooks Air Force Base in Texas showed that dogs exposed to near vacuum—one three-hundred-eightieth of atmospheric pressure at sea level—for up to 90 seconds always survived.

However, dogs held at near vacuum for just a little bit longer—two full minutes or more—died frequently.

In a pair of papers from NASA in 1965 and 1967, researchers found that chimpanzees could survive up to 3.5 minutes in near-vacuum conditions with no apparent cognitive defects, as measured by complex tasks months later. One chimp that was exposed for three minutes, however, showed lasting behavioral changes. Another died shortly after exposure, likely due to cardiac arrest.

And a human engineer:

Houston accidentally depressurized his space suit by disrupting a hose. After 12 to 15 seconds he lost consciousness. He regained it at 27 seconds, after his suit was repressurized to about half that of sea level.

The Soyuz 11 craft depressurized during reentry which resulted in the death of the entire crew:

The valve opened at an altitude of 168 km (104 mi), and the resultant loss of pressure was fatal within seconds. [...] Flight recorder data from the single cosmonaut outfitted with biomedical sensors showed cardiac arrest occurred within 40 seconds of pressure loss.

The exact cause and timing of death varies a lot but it's safe to say survivability is measured in minutes.

Worth noting that you don't freeze to death in space beacause there is no medium to transfer heat away from your body quickly. The causes are lack of oxygen and trauma from pressure changes.

Also, you may survive but have severe brain damage or lose your eyesight, hearing, some limbs etc.

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