If you’re underwater and your small diving tank or any part of your breathing gas system starts to fail, the immediate, non-negotiable procedure is to switch to an alternate air source. This is your absolute priority. The most common and effective method is to use your buddy’s alternate second-stage regulator (the octopus). Signal to your buddy—using the internationally recognized slashing hand gesture across the throat—that you are out of air. Your buddy should immediately provide their alternate air source. Once you are breathing normally, you and your buddy must make a controlled, safe ascent to the surface together, maintaining contact throughout. Do not make a rapid, uncontrolled ascent; this can lead to life-threatening decompression sickness or arterial gas embolism. Ascend at a rate no faster than 30 feet (9 meters) per minute, and make a safety stop at 15-20 feet (5-6 meters) for 3-5 minutes if your air supply and conditions allow.
Recognizing the Signs of a Failing Gas System
An emergency rarely happens without warning. A complete, sudden failure is less common than a progressive issue that a vigilant diver can detect early. Recognizing these signs is your first line of defense.
Changes in Breathing Resistance: If it becomes suddenly harder to inhale (increased inhalation effort) or you feel like you’re fighting the regulator to exhale, this is a critical sign. It could indicate a failing first stage, a malfunctioning second stage, or a nearly empty tank. Conversely, a free-flowing regulator—one that releases a continuous, uncontrolled stream of air—is also a failure. It will deplete your air supply in seconds. The procedure for a free-flow is to try to breathe from it in bursts if possible, but more importantly, to immediately switch to your alternate air source and ascend.
Auditory Cues: Your ears are powerful tools. A persistent, loud hissing sound typically points to a leak in a hose O-ring or a failing first-stage diaphragm. A faint whistling or chirping sound on inhalation might indicate a worn-out second-stage valve. Any unusual metallic grinding or popping noise from the first stage is a serious red flag.
Visual Indicators on Your Gauge: This is why you should check your pressure gauge frequently. A rapid drop in pressure that doesn’t correlate with your breathing rate suggests a major leak. Also, be aware of the tank’s pressure from the start. A standard 80-cubic-foot aluminum tank filled to 3000 PSI (207 bar) should give an average diver about 60 minutes at a depth of 30 feet (10 meters). If your dive time is significantly less, it could indicate a pre-dive issue or an underwater leak.
| Warning Sign | Possible Cause | Immediate Action |
|---|---|---|
| Increased breathing effort | First-stage failure, nearly empty tank, second-stage malfunction | Signal to buddy, switch to alternate air source, begin ascent. |
| Regulator free-flow | Water in second stage, damaged valve seat | Attempt to breathe in bursts, close tank valve momentarily, switch to alternate air, ascend. |
| Rapid pressure drop on SPG | Major hose or O-ring failure | Immediately signal out-of-air, secure buddy’s alternate, begin controlled emergency ascent. |
| Constant hissing sound | Leaking O-ring or first-stage issue | Locate source if safe, monitor air supply closely, end dive early and ascend normally. |
The Critical Steps of an Emergency Ascent
Once you have secured a breathing gas source, the ascent itself is a delicate procedure. Doing it wrong can be as dangerous as the original problem.
Buddy Breathing Ascent: This is the standard. You and your buddy are now a single unit. Maintain physical contact, typically by holding onto each other’s BCD straps or arms. The donating buddy (the one with the working air supply) should hold their alternate second stage for the receiver, allowing for better control. Ascend side-by-side, not one above the other, to maintain equal pressure and avoid dislodging the regulator. Continuously exhale slowly to prevent lung overexpansion injuries. The donating buddy should manage the buoyancy for both divers if necessary.
Controlled Emergency Swimming Ascent (CESA): This is a last-resort procedure if you are without air and your buddy is not reachable. It involves swimming to the surface at a safe pace while continuously exhaling a long, steady “Ahhhhh” sound. This open airway is essential to allow expanding air to escape your lungs. The recommended maximum depth for a CESA is 30-40 feet (9-12 meters). Any deeper, and the risk of air starvation and decompression illness increases dramatically. The ascent rate should be no faster than you can comfortably exhale.
Using a Surface Marker Buoy (SMB) or Deploying a Dive Alert: If you have the presence of mind and a free hand, deploying a delayed surface marker buoy (DSMB) during your ascent alerts boat traffic to your position. Similarly, as you break the surface, immediately activate an auditory alert device, like a whistle or a battery-powered dive alert, to signal for help. Your primary concern is breathing, but if you can manage these secondary actions, they significantly enhance surface safety.
Pre-Dive Prevention: The Key to Avoiding Emergencies
The best emergency procedure is the one you never have to use. Rigorous pre-dive checks are non-negotiable for safe diving.
The BWRAF Buddy Check: This acronym is drilled into every certified diver for a reason. It’s a systematic check of both your gear and your buddy’s gear before entering the water.
- B (BCD): Inflate and deflate your BCD to ensure no leaks and that the dump valves work.
- W (Weights): Confirm your weight system is secure and you know how to release it in an emergency.
- R (Releases): Check all buckles and clips on your BCD and harness.
- A (Air): This is the most critical part. Turn on your tank. Breathe from your primary regulator and your alternate regulator. Check that the pressure gauge reads a full fill (e.g., 3000 PSI or 207 bar for an AL80). Check for leaks by listening for hissing around the tank valve, first stage, and hoses.
- F (Final Okay): Do a visual check of your buddy’s gear and give a final signal that you are both ready.
Regular Equipment Servicing: Regulators and tank valves are complex pieces of precision engineering. They must be serviced annually by a qualified technician, or more frequently if you dive in harsh conditions (cold water, silt, etc.). A typical service involves disassembly, cleaning, replacement of O-rings and wear-prone parts, lubrication, and reassembly with pressure testing. Skipping service to save money is a false economy that risks your life.
Understanding Your Tank’s Vital Statistics: Not all tanks are the same. Knowing your tank’s capacity and working pressure is fundamental to dive planning. The most common tank for recreational diving is the AL80, but smaller tanks like a 63-cubic-foot or a 50-cubic-foot tank have significantly less air. Your dive plan, including depth and time, must be tailored to your specific gas volume.
| Tank Type (Common Sizes) | Capacity (Cubic Feet) | Working Pressure (PSI / Bar) | Approx. Bottom Time at 60ft/18m* |
|---|---|---|---|
| Aluminum 80 (AL80) | 80 cu ft | 3000 PSI / 207 bar | 25-30 minutes |
| Aluminum 63 | 63 cu ft | 3000 PSI / 207 bar | 20-25 minutes |
| Steel 100 | 100 cu ft | 3442 PSI / 237 bar | 35-40 minutes |
*Estimate for an average diver with a resting respiratory rate; actual time varies based on exertion, stress, and physiology.
Post-Emergency Protocol and Gear Inspection
What you do after you surface safely is just as important. An emergency doesn’t end when you get back on the boat.
Medical Assessment: Even if you feel fine, any emergency ascent, especially a CESA or a rapid ascent, warrants a medical evaluation. Symptoms of decompression sickness (DCS) or lung barotrauma can be delayed. Inform the dive master or your emergency contact about the incident. Monitor yourself and your buddy for symptoms like fatigue, joint pain, dizziness, shortness of breath, or paralysis for at least 24 hours. If any symptoms appear, seek immediate hyperbaric medical attention.
Gear Quarantine and Professional Inspection: The failed equipment must be taken out of service immediately. Do not attempt to use it again until it has been thoroughly inspected and repaired by a certified professional. Mark the tank and regulator set clearly (e.g., with a tag that says “FAILED – DO NOT USE”) to prevent accidental use by yourself or others. The technician will need to diagnose the root cause—whether it was a manufacturing defect, a service error, or damage incurred during the dive.
Incident Reporting and Mental Debriefing: File a detailed incident report with the dive operator and your training agency (PADI, SSI, etc.). This data helps improve safety standards for all divers. Furthermore, discuss the event calmly with your buddy and an instructor. This mental debriefing is crucial for processing the stress and reinforcing the correct procedures, ensuring you are mentally prepared to dive again in the future.