Making a safe ascent with a buoyancy compensator (BC) depends on how the equipment is used. Six techniques for ascending safely with the use of a BC is presented. These include signaling and checking instruments with a diving buddy before attempting to ascent, attaining neutral buoyancy before leaving the bottom, venting the BC while ascending, monitoring the rate of ascent, controlling the ascent with the BC and staying alert during the ascent.
Like any tool, the BC is neither safe nor dangerous. It’s how you use it that makes it so.
It’s hard to imagine, but in the early days of BC use, divers worried that BCs would cause out-of-control ascents and rocket them to the surface. Naysayers attacked power inflators as being “push-button, elevator diving,” contending that safe diving meant surfacing without using the BC’s power inflator.
Many of these dinosaurs were unfortunately also underwater instructors. They taught student divers to dump all the air from their BCs before ascending and then to swim up against negative buoyancy. The muddled logic of this training was that swimming hard would prevent out-of-control ascents. Yet leading underwater physiologists have for years told us to reduce mental and physical stress as much as possible, particularly during the crucial time of ascents.
So what’s a modern diver to do? Here is the latest and best thinking on this crucial aspect of BCs and their use.
Table of Contents
SAFE ASCENTS: A 6-Step Plan
- COMMUNICATE. Signal to your buddy before leaving the bottom, then check the environmental conditions, check with each other and check your instruments.
- GET NEUTRAL. Become neutrally buoyant with the use of your BC power inflator before leaving the bottom.
- VENT. Be ready to vent your BC slowly while gently kicking to ascend.
- MONITOR. Use your instruments to check your rate of ascent. Below 60 feet, a faster rate is appropriate to move you more quickly out of the depth range where nitrogen is still in-gassing. From 60 to 30 feet, a rate of 60 feet per minute slows you down, yet is still controllable. At 30 feet, use the extremely slow rate of 30 feet per minute. Because this rate is so slow, it can be difficult to control. Find a reference such as the anchor line, kelp or the slope of the bottom to help control your ascent.
- USE IT. Control your ascent with the BC. This slow rate of ascent can also help you be in control as you arrive at your safety stop. Again, having a reference will be very helpful. Even though we’re taught to make safety stops for three minutes at 15 feet, it is perfectly reasonable to use a range of 10 to 20 feet and stay until your dive computer is out of any caution zone.
- STAY ALERT. Ascending slowly under control not only reduces the risk of air embolism and decompression sickness, but it also reduces the likelihood that you might hit a boat, become entangled in lines or kelp or lose buddy contact. In addition, slow ascents reduce stress and allow you to adapt to changing conditions.
OUT-OF-CONTROL ASCENTS: When All Else Fails
If you, through human error or malfunction, should ever have an out-of-control ascent, don’t panic. Instead:
* Immediately relax, breathe easy and look up.
* Dump all air from your BC with the quickest available method; this usually means using the remote exhaust on the shoulder, but on some BCs the quickest method is to use the oral deflate.
* If you are still ascending, flare your body by throwing your shoulders back, spreading out your arms and legs while looking up at the surface.
Once under control, it’s time for some self-assessment. If the ascent was caused by a malfunction of the BC inflator, carefully attempt to correct it. If it was diver error, which is far more likely, take more care, particularly when you are moving into shallower water with air in your BC.
MORE BC INSIGHTS
Based on thousands of individual tests, here are some additional insights concerning BCs.
* The easy way in. The assembling and adjusting of BCs can be made considerably easier.
* First, wet the BC’s tank bands.
* Then lay the BC face-down on the deck and slide the tank into the bands. This is much easier than trying to place the BC on the tank while it is standing, and this will also allow you to cinch the tank bands more securely.
* If there is a stabilizer band in addition to the primary tank band, secure it tight first.
* If you are using a primary tank band of the most common generic type – unthread it from only the last notch in the buckle and pull it snug, then thread the loose end through the buckle and use this tag end as a lever to pull the buckle closed.
* When you’re ready to put the assembled scuba unit on, place it on a bench and slip into it with shoulder straps loose and the other closures and straps open.
* Tighten your waistband and overstraps first, then the shoulder straps. The shoulder straps can be further adjusted after entering the water.
* Use rear-facing pockets properly. Many BCs have open pockets that face the rear on both sides. These pockets are not for keeping loose items, but can be used to hold secondary regulators and instruments.
Still Having Problems? Check These
* By using a BC of the correct size and lift capacity, you are far more likely to be able to control your ascent.
* By weighting for neutral buoyancy, you will also be better able to control your ascents. The ultimate buoyancy check: you should use the smallest amount of weight you need to remain neutral at 15 feet with no air in your BC and only a reserve of air in your primary tank.
* Our tests show that a diver will achieve a maximum ascent rate that can be cut in half by flaring – spreading out your arms and legs and looking up at the surface.
* Tests also show that out-of-control ascents can be stopped with the use of the BC, provided the loss of control occurs deeper than about 15 feet, thus providing you the time and distance to react and have your action take effect.
Face-Up Floating: Let’s Settle This Once and for All
There’s a school of thought that says all BCs should float an unconscious diver face-up on the surface. Those who say it should go back to school. Here are the facts:
It is clear that there is no BC that will, of its own accord, consistently float a scuba diver face-up. There are just too many variables, including:
- The BC: type, size, lift capacity and amount of inflation.
- The tank: size, buoyancy and amount of air in it
- The diver: size, body build and personal buoyancy.
- The starting position: under water or on the surface; diver on side, on back, on front or vertical.
- The protective suit: wet, dry or skin; type and coverage.
- The surface water conditions: rough or calm; swells or chop.
- The weight system: amount and distribution.
That’s right: each of those variables interact with the others to produce or not produce face-up floating in an inconsistent, unpredictable manner. However, there are trends:
- Divers with poor-fitting BCs, back-buoyancy BCs or with standard aluminum 80-cubic-foot tanks, particularly when low on air, will more likely float on their sides or face-down.
- Even when divers do float face-up, their mouths may not be above the surface of the water.
- Divers are far more likely to float face-up if weights are moved to the rear on the belt or in the BC; if the BC’s trim weights or other tank-mounted weights are used; or if negatively buoyant tanks are used.
- Adding weights toward the diver’s back will decrease the diver’s underwater stability and increase the diver’s likelihood of being turned turtle while under water.
It is common to find on BC labels and in BC instructions a statement similar to this: “This is not a life jacket; it does not guarantee a head-up position of the wearer at the surface.”
BOTTOM LINE: A BC is for buoyancy control throughout a dive; a life jacket is only for emergency flotation at the surface. The very characteristics that make a life jacket work are counterproductive in a BC.
One last point about face-up floating: Even if an unconscious diver were to float face-up with mouth and nose out of the water, survival is unlikely unless someone else is there to ditch gear, give rescue breaths and tow the victim to safety.