Decompression and oxygen systems
Why cabins are pressurised, what decompression means, and how oxygen systems respond.
Aircraft cabins are pressurised because the air at cruising altitude is too thin to breathe comfortably; pressurisation keeps the cabin at an equivalent altitude passengers can tolerate without extra equipment.
A decompression is a loss of that cabin pressure, which can be gradual or rapid. In either case, oxygen masks drop automatically above a set cabin altitude, and passengers are instructed to secure their own mask before helping others.
Crew are trained to recognise decompression symptoms and to follow oxygen and descent procedures — general audiences should understand the 'why', while the exact drills stay part of type-specific crew training.
Key points
- Cabins are pressurised because high-altitude air is too thin to breathe unaided.
- Oxygen masks drop automatically above a set cabin altitude.
- Secure your own mask first, then help others.
Vocabulary
- Cabin altitude
- The equivalent altitude the pressurised cabin simulates, typically around 6,000–8,000 feet at cruise.
- Rapid decompression
- A sudden loss of cabin pressure, distinct from a slower, gradual loss.
Remember this
Educational overview only — always follow the current airline/operator procedures and approved training.