Supplemental Oxygen Requirement Checker (14 CFR 91.211)
Enter your cabin pressure altitude and planned time — get the FAA Part 91 oxygen requirements for crew and passengers, decided correctly.
These are Part 91 minimums — many operators and physiologists use oxygen from 10,000 ft by day and 5,000 ft at night, where night vision measurably degrades.
Formula
⚠️ For flight planning and education only — always verify against your aircraft's POH/AFM, official weather sources and certified instruments. Not for primary navigation or airworthiness decisions.
Enter your cabin pressure altitude and planned time — get the FAA Part 91 oxygen requirements for crew and passengers, decided correctly.
About Supplemental Oxygen Requirement Checker (14 CFR 91.211)
The Part 91 oxygen rule is short, but pilots still mix up its three thresholds under quiz pressure — 12,500, 14,000 and 15,000 ft cabin pressure altitude, with a 30-minute clock attached to the first. This checker applies 14 CFR 91.211 to your cabin altitude and exposure time, states the requirement for crew and passengers separately, and adds an estimated blood-oxygen saturation figure to explain why the physiologists' personal minimums sit far below the legal ones.
How to use Supplemental Oxygen Requirement Checker (14 CFR 91.211)
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula 91.211: crew O₂ — >12,500 ft after 30 min; >14,000 ft always. Passengers provided O₂ — >15,000 ft substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Supplemental Oxygen Requirement Checker (14 CFR 91.211)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula 91.211: crew O₂ — >12,500 ft after 30 min; >14,000 ft always. Passengers provided O₂ — >15,000 ft with sources cited on the page
- ✓These are Part 91 minimums — many operators and physiologists use oxygen from 10,000 ft by day and 5,000 ft at night, where night vision measurably degrades.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
What exactly does 14 CFR 91.211 require?+
Three layers, all in cabin pressure altitude: above 12,500 ft up to 14,000 ft, required minimum flightcrew must use oxygen for any portion beyond 30 minutes; above 14,000 ft, crew use it for the entire time; above 15,000 ft, every occupant must be provided oxygen (passengers needn't use it — it must be available).
Why is the rule written against cabin altitude, not aircraft altitude?+
Because hypoxia follows the pressure your lungs see. In an unpressurized aircraft the two are identical; in a pressurized one the cabin may sit at 8,000 ft while the airframe cruises at FL250 — no oxygen required. Lose pressurization and the cabin altitude (and the rule) snaps to the flight altitude immediately.
How low can blood oxygen drop at 12,500 ft without supplemental O2?+
A healthy unacclimatized adult typically falls to 88–92% SpO₂ at 12,500 ft, from ~97% at sea level — enough to dull night vision, arithmetic and judgment subtly. Smokers, fatigue and illness push it lower. The legality of flying there for 30 minutes doesn't make the cognitive tax zero, which is why many pilots carry a pulse oximeter.
Are the rules different at night?+
Legally, no — 91.211 has no day/night distinction. Physiologically, yes: the retina is the body's most oxygen-hungry tissue, and night vision degrades measurably from about 5,000 ft cabin altitude. The FAA's own physiology guidance (AC 61-107B and AIM 8-1-2) recommends oxygen above 5,000 ft at night, a far more conservative line than the regulation.
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