One of the first things that is drilled into your minds when you begin scuba diving is the importance of a safe ascent from depths. And why?
It all boils down to the physics of diving and Boyle’s Law. While usually, nitrogen is expelled from a person’s body during an exhale and through their skin, when breathing compressed air because of the ambient water pressure, the nitrogen absorbed remains in the body’s fatty tissues and blood. The longer and deeper the dive, the more nitrogen is absorbed into the tissues. As long as the diver remains at pressure, the gas presents no problem. However, when the pressure around the diver decreases the nitrogen starts coming out of the tissues back into the blood stream. If the pressure is reduced too quickly, i.e when the water pressure decreases when ascending, the nitrogen starts forming bubbles in the tissues and bloodstream rather than being exhaled just like when you open a bottle or can of soda releasing the pressure which causes the carbon dioxide gas to lose its solubility and escape in the form of bubbles or fizz. This is what we all know as ‘The Bends’ or Decompression Sickness (DCS).
So What’s Qualifies as a Safe Ascend?
What seems like a trivial question is probably one of the most asked and debated about in diving. Some scuba organizations state that divers should ascent faster than a maximum of 18m/60ft per minute. However, this absolute maximum has still resulted in divers getting the bends in some cases. Today, a more generally accepted safe ascent rate by scuba organizations and most dive computers is 9m/30ft per minute. More simply put for divers without a dive computer (which we don’t recommend) is to follow your smallest air bubbles. That said, we believe you should always dive with a dive computer for each diver that allows you to monitor depth and speed and also alerts you when ascending too fast (a standard feature in most dive computers these days).
How to Complete a 5 Point Safe Scuba Ascent
Remember the Acronym S.T.A.R.S (as taught in the PADI Open Water Course) and it get it wrong.
S- SIGNAL: Give the clear ready to start ascending signal (thumb up hand signal) and receive a confirmation from all divers that they are aware the dive is ending.
T-TIME: Look at the time indicated on your dive computer to make sure the No-decompression limit wasn’t exceeded. If exceeded prepare to make decompression stops at recommended depths and signal to your buddy diver for a confirmation. Time and fully complete your safety stop.
A-AIRWAY: Look up and make sure there’s a direct path to the surface. Search for obstacles (like boats you won’t want to bonk your head on).
R-REACH: Extend your arm above your head signaling the okay signal to the boat or fellow divers at the surface and to protect hitting your head on anything that may be above you. Turn around when ascending to keep track of anything behind you.
S- SWIM- Swim very slowly to the surface not using your BCD (Buoyancy Control Device) to ascend until you surface. Once at the surface you may inflate your BCD to help keep you buoyant.