One of the most critical aspects of a successful dive is the ascent. Improper surfacing techniques can lead to a variety of health risks, including decompression sickness (DCS), also known as “the bends,” and barotrauma. This guide covers the best practices for ascending, the physiology behind safe surfacing, and common mistakes divers should avoid.
- Safe surfacing procedures apply to all dives using compressed air, including SCUBA and surface-supplied air.
- A safety stop at 5 metres is mandatory for dives deeper than 18 metres or those approaching the no-decompression limit.
The Importance of a safe ascent
1. Decompression sickness (DCS)
When divers spend time at depth, their bodies absorb nitrogen from the breathing gas. Ascending too quickly can cause this nitrogen to come out of solution too rapidly, forming bubbles in the bloodstream and tissues, leading to decompression sickness. DCS can result in joint pain, paralysis, or even death if not treated promptly.
2. Preventing Barotrauma
Barotrauma occurs when pressure changes during ascent cause damage to body tissues, most commonly the lungs or ears. Slow and controlled ascents allow the diver’s body to equalise with the surrounding pressure, preventing injury.
Best practices for a safe ascent
1. Monitor your ascent rate
- Ascent rate: The safe ascent rate is calculated by your dive computer and should be adhered to. However, if no dive computer is available divers should ascend no faster than 9-10 meters (30 feet) per minute. This slow rate ensures that nitrogen can safely be released from the body’s tissues without forming harmful bubbles.
- Use a Dive Computer: A dive computer is an essential tool for monitoring your ascent rate. Most dive computers will alert you if you are ascending too quickly, allowing you to adjust accordingly.
2. Conduct a safety stop
- Safety stops: Performing a minimum safety stop at 5 meters (15 feet) for 3-5 minutes is best practice, especially for dive profiles that exceed no-decompression limits. This stop allows excess nitrogen to off-gas and provides an additional safety margin, particularly after deep or prolonged dives. Longer, deeper dives may require longer safety stops - check dive tables and your computer for guidance.
- Importance of safety stops: Even if your dive profile is within the no-decompression limits, a safety stop is a good habit to develop. It adds an extra layer of safety to your dive routine.
3. Equalise pressure during ascent
- Ear equalisation: Equalise your ears frequently during ascent to prevent pressure building up.
- Lung protection: Never hold your breath while ascending. Always breathe continuously to prevent potentially fatal overexpansion injuries to the lungs.
4. Maintain buoyancy control
- Buoyancy Compensator Device (BCD): Use your BCD to control buoyancy gradually during the ascent. Avoid dumping all your air or inflating it rapidly, as this can lead to an uncontrolled ascent. These are essential skills learned during a dive course.
- Body position: Ascend in an upright position to maintain better control of your buoyancy and to keep an eye on your dive computer and surroundings.
Using the Buddy System during ascent
1. Ascend together
- Stay close: Maintain visual contact with your buddy throughout the ascent. Ascending together ensures that if an emergency arises, such as an out-of-air situation, you can quickly assist each other.
- Communication: Use hand signals to communicate your ascent intentions and confirm with your buddy when it's time to begin ascending or conduct a safety stop.
2. Monitor each other
- Ascent rate: Keep an eye on each other’s ascent rate to ensure that neither of you is ascending too quickly.
- Buoyancy checks: Assist each other in maintaining proper buoyancy, especially during the safety stop when fine adjustments may be needed.
Common mistakes to avoid during ascent
1. Ascending too quickly
- Danger of rapid ascents: Ascending faster than the recommended rate can increase the risk of decompression sickness. Always monitor your dive computer and listen to its alarms to ensure a controlled ascent.
2. Skipping the safety stop
- Consequences: Skipping the safety stop, especially after a dive that exceeds no-decompression limits, can put you at higher risk for DCS. Even if you feel fine, the safety stop allows your body to expel excess nitrogen.
3. Over-inflating the BCD
- Uncontrolled ascents: Rapidly inflating your BCD can lead to an uncontrolled ascent, which is dangerous for both you and your buddy. Instead, make small adjustments to your buoyancy as you ascend.
4. Holding your breath
- Risk of lung overexpansion: Never hold your breath while ascending. Expanding air in your lungs due to decreasing pressure can cause serious injuries, including ruptured alveoli (air sacs) or arterial gas embolism.
The Role of Dive Computers in Safe Surfacing
1. Monitoring Ascent Rate
Dive computers are invaluable tools for maintaining a safe ascent. They calculate your depth, time, and rate of ascent, alerting you if you exceed safe limits. Make sure your computer is in good working condition before every dive.
2. Decompression Warnings
If you exceed no-decompression limits, a dive computer will guide you through the necessary decompression stops. Follow its instructions carefully to avoid DCS.
Emergency Ascent Techniques
1. Controlled Emergency Swimming Ascent (CESA)
- When to Use: A CESA is used when you are out of air and cannot reach your buddy. Ascend slowly while continuously exhaling, using controlled fin kicks to reach the surface safely.
2. Buddy Breathing
- Air Sharing: In an out-of-air situation, your buddy’s alternate air source becomes your lifeline. Practice air-sharing drills regularly so that both you and your buddy can respond calmly and effectively if the need arises.
Conclusion
Safe surfacing procedures are a crucial part of every dive. By maintaining a slow ascent rate, using your dive computer, performing safety stops, and staying in close contact with your buddy, you can significantly reduce the risks of decompression sickness and other diving-related injuries. Always remember: ascending slowly and safely is just as important as any other part of your dive. Taking the time to do it right ensures that you can continue enjoying your underwater adventures for years to come.
