Safety
What Happens If You Run Out of Air?
It almost never happens — and when it does, there's a simple, practised procedure to handle it.
Running out of air should never happen — you carry a pressure gauge (SPG) and begin your ascent before reaching 50 bar / 500 psi. But if it does, you stay calm, share air from your buddy's backup regulator (the "octopus"), and make a slow, controlled ascent together. It's a core skill every diver practises.
- Prevention
- Watch your SPG
- Start ascent by
- 50 bar / 500 psi
- If it happens
- Share your buddy's octopus
- Then
- Ascend slowly together
First — it shouldn't happen
Modern diving is built to prevent this. You constantly monitor your submersible pressure gauge (SPG), plan your turnaround pressure, and begin heading up well before your tank gets low — typically starting your ascent at 50 bar / 500 psi, leaving a comfortable reserve. Good gas management means you finish every dive with air to spare.
The key to never being surprised is knowing your air consumption rate — your personal SAC (surface air consumption). Once you know how fast you breathe, you can predict exactly how long a tank will last at a given depth, and set a safe turnaround pressure before you ever get in the water.
Know your numbers before you dive. The Diving Standard app includes a Gas & SAC planner that calculates your air consumption and tells you precisely how long your tank will last at depth — and your turnaround pressure — so running low stays a theoretical worry, not a real one.
If you do run low or out of air
There's a calm, practised procedure for exactly this. You learn and rehearse it in your certification course:
- Signal your buddy: Give the 'out of air' hand signal (a hand drawn across the throat) and move to your buddy.
- Take their alternate regulator: Every diver carries a backup second stage — the 'octopus' — exactly for this. Your buddy donates it (or you take it) and you breathe normally.
- Get stable and breathe: Hold onto each other, settle your breathing, and confirm you're both okay.
- Ascend slowly together: Make a slow, controlled ascent as a team, doing a safety stop if your air allows. Never hold your breath.
Never hold your breath, and never bolt for the surface. A controlled ascent — sharing air with your buddy — is always safer than a panicked rush. This is precisely why we dive with a buddy and rehearse air-sharing until it's second nature.
Other backups divers use
- Buddy system — your primary backup air source is always your buddy.
- Pony bottle — a small independent tank some divers carry for full redundancy.
- Controlled emergency swimming ascent (CESA) — a last-resort, single-breath ascent from shallow depths, taught in your course.
Calculate your air consumption
Never be caught out. The Diving Standard app's Gas & SAC planner calculates your personal air consumption and how long your tank will last at depth — plus free lessons on gas management and air-sharing.
Get the Diving Standard appFrequently asked questions
What do you do if you run out of air underwater?
Signal your buddy, breathe from their alternate regulator (octopus), get stable, and ascend slowly together — never holding your breath. It's a standard, rehearsed skill.
How do divers avoid running out of air?
By monitoring the pressure gauge throughout the dive and beginning the ascent before reaching about 50 bar / 500 psi, always keeping a reserve.
What is an octopus in scuba diving?
The octopus is your regulator's backup second stage — a spare mouthpiece your buddy can breathe from if they run low on air. Every recreational diver carries one.