Hypoxia (exploration atmosphere)
Also: Hypoxia risk
Hostile/Closed EnvironmentPulmonaryNeurological & CognitiveIn-flightEVA & Surface OpsLunar surfaceMars transit & surfacePublicClinicianResearcher
- The proposed 8.2 psia / 34% O₂ atmosphere is mildly hypoxic, similar to living at about 4,000–8,300 ft. ◆◆◆◇ Moderate · F E
- Short exposures are well tolerated, based on 40 Shuttle missions. Effects over many months are uncharacterized. ◆◆◇◇ Low · F E
Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.
NASA risk title (verbatim)
Risk of Reduced Crew Health and Performance Due to Hypoxia
NASA short title: Hypoxia · HRP element: Human Health Countermeasures (HHC) · Status: Active [current research ongoing] [1]
What it is
Lowering cabin pressure shortens the oxygen pre-breathe needed before a spacewalk, but it means slightly less oxygen is available to the body. This risk covers the health and performance effects of that mild hypoxia [1].
Current evidence
- The proposed exploration atmosphere is 8.2 psia with 34% oxygen. It was chosen as mildly hypoxic, with acceptable fire risk and a short pre-breathe [1].
- In oxygen availability it is similar to the 10.2 psia, 26.5% oxygen atmosphere used for staged decompression on 40 Shuttle missions of 1–8 days. Both are modeled as equivalent to altitudes of about 4,000–8,300 ft [1].
- The main concerns are intracranial pressure, vision, cognition, sensorimotor function, oxidative damage and sleep. Acute mountain sickness is also studied [1].
- For the lunar lander program, NASA extended its 7-day limit for mildly hypoxic environments to 30 days with monitoring [1].
NASA’s risk posture
NASA scores each risk for each design reference mission (DRM) as likelihood × consequence (LxC). Both run from 1 (lowest) to 5 (highest) on the HSRB’s 5×5 matrix [1][3]. Each score comes with a disposition, such as “Accepted”, “Requires Characterization” or “Requires Mitigation”. These ratings were last approved by NASA’s Human System Risk Board (HSRB) in 11/2022 [1].
| Mission | Duration | In-mission (operations) | Long-term health |
|---|---|---|---|
| LEO | Short (under 30 d) | 3x2 · Accepted with Monitoring | 2x1 · Accepted |
| LEO | Long (30 d–1 yr) | 3x2 · Accepted with Monitoring | 2x2 · Requires Characterization |
| Lunar orbit | Short | 3x2 · Accepted with Monitoring | 2x1 · Accepted |
| Lunar orbit | Long | 3x2 · Accepted with Monitoring | 2x2 · Requires Characterization |
| Lunar orbit + surface | Short | 3x2 · Accepted with Monitoring | 2x1 · Accepted |
| Lunar orbit + surface | Long | 3x3 · Accepted with Monitoring | 2x2 · Requires Characterization |
| Mars preparatory | Under 1 yr | 3x3 · Accepted with Monitoring | 2x2 · Requires Characterization |
| Mars planetary | 730–1,224 d | 3x3 · Accepted with Monitoring | 2x2 · Requires Characterization |
This risk has no gaps of its own. Its research is carried under the EVA risk [1].
Copied from the Human Research Roadmap on 2026-10-14. Ratings change. Check the live record before citing.
Open knowledge gaps
NASA lists no gaps under this risk. Its research questions are tracked under the EVA risk [1].
See also Open questions.
Active countermeasure research
- Research. Studies of responses to hypobaric hypoxia, and to cycling between mild hypoxia and mild hyperoxia during spacewalks, are managed under the EVA risk strategy [1].
Project-level detail, including status, investigators and results, is in the NASA Task Book and on each HRR gap page.
Clinical articles
For practical, clinic-facing guidance, see:
Evidence profile
- Overall certainty
- ◆◆◇◇ Low (proposed)
- Evidence types
- F · Flight dataE · Expert / operational / standards
- Literature through
- 2026-10-14
- NASA source
- Human Research Roadmap risk page (last published 05/13/25; read 2026-10-14)
Requirements referenced 2
| Requirement | Title | Plain-language meaning |
|---|---|---|
| [V2 6006] | Total Pressure Tolerance Range for Indefinite Crew Exposure | Cabin total pressure kept within a range tolerable indefinitely (5–15 psia). |
| [V2 6007] | Rate of Pressure Change | Limits how fast pressure may change (no more than 13.5 psi/min). |
IDs as published in NASA-STD-3001 Vol. 1 Rev C (2023-09-15) and NASA-STD-3001 Vol. 2 Rev F (2026-07-14). NASA-STD-3001 binds NASA programs; it is not a regulation for commercial flights. Paraphrased. Standards quick reference.
References 3
- NASA Human Research Roadmap. Risk record: “Risk of Reduced Crew Health and Performance Due to Hypoxia”. Accessed 2026-10-14. humanresearchroadmap.nasa.gov/Risks/?i=173 NASA E
- NASA Human Research Program. Evidence report for the Hypoxia and DCS risks (approved October 31, 2023). humanresearchroadmap.nasa.gov/evidence/reports/Evidence%20Re… NASA E
- Antonsen EL, et al. Updates to the NASA human system risk management process for space exploration. NPJ Microgravity. 2023;9:72. doi:10.1038/s41526-023-00305-z PMID:37679359 Peer-reviewed E
Machine-checked on 2026-10-14: each URL resolved, each DOI's title/journal/year matched via Crossref, and claims were checked against the source text (abstract or full NASA page). Human verification against full text is still required before review. NASA documents are U.S. Government works (public domain) and are summarized with attribution; journal articles are summarized, not reproduced.
Article info
- Authors
- Pending (AI-assisted draft)
- Reviewer
- Pending review
- Last reviewed
- Pending review
- Literature through
- 2026-10-14
- AI-assisted
- Yes (disclosed)
- COI
- Pending
- License
- CC BY-SA 4.0
- Use
- Educational only · Disclaimer
- Cite this version
- Pending first edition