Thursday 15 November 2012

10 New Rules of Scuba Diving


1. Reverse Dive Profiles Are OK

New Rule
It is permissible to dive deeper on your second dive than on your first, and to dive deeper on the later part of a dive than on the early part.

Old Rule
Until this year, all divers have been taught to go to their greatest planned depth early in the dive and then gradually work upward in a regular "stair-step" pattern. Similarly, they've been told to make the deepest dive of the day the first one. The rationale was that the shallower depths later provided decompression for the preceding greater depths.

Reason for the Change

Dive computers. Because computers can track your depth and time constantly and are pretty good at math, it's possible to know your nitrogen exposure accurately regardless of your profile. Tables, by contrast, can account for only your greatest depth, and this crude approximation of nitrogen exposure still mandates a conservative approach.

Exceptions to the Rule

Obviously, divers using only tables must still follow the old rules. And even when using a computer it's still smart to dive deeper first. Ascending profiles give you more bottom time and a greater margin of safety against DCS.

2. Lower Minimum Age

New Rule

The Recreational Scuba Training Council, which sets many industry standards, dropped its minimum age requirement for junior certification near the end of 1999. As a result, PADI, SDI, SSI and NASDS (which has merged with SSI) have dropped their minimum age requirements for junior certification to 10. SSI has a pool-only "Scuba Ranger" program for 8- to 12-year-olds. NAUI and YMCA are retaining the age-12 minimum, at least for now.

Old Rule

Minimum age for junior certification was 12. (Junior certification requires supervision by a fully certified adult.)
 
Reason for the Change

To promote the sport. Lots of baby-boomer divers have kids, and the growing popularity of resort diving meant a market for family dive vacations. "The future of diving will be determined by kids," says Bret Gilliam, president of SDI, the first agency to lower the age. "It's a great step forward to recognize the family unit as key to our sport's growth."

Exceptions to the Rule

It's still up to the instructor to decide whether a child is mature enough to dive. Being 10 does not create a right to be certified.
The new junior certifications typically have various restrictions. In PADI, kids are limited to 20 feet in confined water first, then 40 feet in open water. Juniors must be accompanied by an agency-affiliated instructor, a certified parent or another certified adult. Check specific agencies for their rules.

3. Universal Referrals

New Rule
Getting certified? Beginning in 1998, you could take classroom and pool sessions in your hometown from an instructor with Agency "A," then fly to warm water for open-water sessions under an instructor with Agency "B"—as long as the agencies had agreements to recognize each other's standards and instructors. This means you can choose from many more warm-water resorts for your open-water sessions.

Old Rule
Classroom, pool work and open-water dives all had to be with the same training agency. If you wanted to do the open-water dives in the tropics, you had to pick a resort with an instructor affiliated with the same agency.

Reason for the Change
Customer convenience. Smaller agencies with few instructors in place at resorts found it necessary to band together to offer greater options—especially when certification standards are virtually identical.

Exceptions to the Rule
PADI. According to PADI, it issues 70 percent of all certifications. The agency still requires that all phases of your training be with PADI instructors.

4. Slower Ascent Rate

New Rule

Ascend no faster than 30 feet per minute—one foot every two seconds.

Old Rule

The usual rate was 60 feet per minute until the U.S. Navy adopted the 30-foot-per-minute rate in 1996 and training agencies followed suit.
Reason for the Change

Research. Navy studies found that a 30-foot-per-minute rate resulted in fewer cases of DCS than the older 60-foot-per-minute rate. A slow ascent is really a rolling decompression stop, allowing your body to flush out and exhale dissolved nitrogen before it forms bubbles.

Exceptions to the Rule
The 30-foot-per-minute rate may not always be practical for the whole ascent, especially when you are deep and low on air or approaching hypothermia. In that case a faster rate, up to 60 feet per minute, is acceptable, but for the final 60 feet of your ascent, you should slow to 30 feet per minute.

5. The Safety Stop

New rule - Make a safety stop at 15 feet for at least three to five minutes before ascending to the surface?longer for deeper and more strenuous dives. Safety stops allow your body extra time to eliminate nitrogen.
New Rule

Make a safety stop at the end of dives. That means you should pause at about 15 feet for a minimum of three to five minutes before your final ascent to the surface. Some experts recommend safety stops as long as 10 to 15 minutes under certain conditions.

Old Rule
Make a what? Safety stops were not taught prior to the mid-1980s.

Reason for the Change
More research. The new rule recognizes that all dives are decompression dives, and that DCS can and does occur even when you've stayed within so-called "no-decompression limits." Studies clearly show that pausing at about 15 feet allows you to offgas nitrogen before ascending through the zone of greatest pressure change, near the surface. Nitrogen that hasn't been eliminated can bubble out of tissues rapidly during the last part of the ascent, causing DCS.
There are other safety reasons for the stop. The air in your BC and the bubbles in your wetsuit also expand rapidly during the last 15 feet and may cause you to become significantly positive without realizing it. Stopping gives you a chance to adjust your buoyancy so you don't lose control of your ascent.
Safety stops also allow you to survey surface conditions and boat traffic before surfacing.

Exceptions to the Rule
You needn't stay at exactly 15 feet, especially if you're elbowing a crowd of other divers. Anywhere between 10 and 20 feet is fine. And although three to five minutes is a good minimum, longer, deeper dives call for longer safety stops.

6. Neutrally Buoyant Ascents

New rule - Remain neutrally buoyant during ascents. Neutral buoyancy eliminates the risk of run-away ascents and the strain of finning against negative buoyancy.
New Rule
Become neutrally buoyant before beginning your ascent and maintain neutral buoyancy throughout.

Old Rule
Dump all air so you are negative before beginning your ascent and fin upward against negative buoyancy.

Reason for the Change
The old rule was designed to prevent runaway ascents. But Navy studies revealed that the strain of finning hard while ascending sometimes causes divers to hold their breath. Also, it can lead to air trapping in the lungs. Both present embolism risks. The change also reflects greater confidence in modern BCs, particularly their dump valves.

Exceptions to the Rule
In an ascent from very shallow depths, say 30 feet or less, it's OK to fin up against slight negative buoyancy. The risk of losing control because of rapid buoyancy changes in your BC and exposure suit, and the low stress in finning such a short distance, makes this the better bet.

7. No More Buddy Breathing

New Rule

In a no-air emergency, depend on a redundant system or your buddy's octopus, or make an independent emergency ascent. Do not attempt to "buddy breathe" from a single regulator unless you and your buddy have practiced it.

Old Rule
Before octos, ponies and devices like the "Spare Air" were common, divers were taught to pass one regulator back and forth while making a slow ascent.

Reason for the Change
Safety. Experience showed that unless both buddies had practiced buddy breathing and were skilled at it, the attempt was likely to injure both divers, not just one.
Typically, buddy breathing divers become so absorbed in passing the regulator that they neglect to control their buoyancy, and a too-rapid ascent with embolism could result. Or the diver who has passed the regulator holds his breath instead of exhaling slowly, also an embolism risk.
If you are out of air and neither you nor your buddy has a backup system, your best move is to make an emergency swimming ascent: swimming to the surface while keeping your throat open by slowly exhaling.

8. The Buddy System

Every training agency is emphatic on the need to always dive with a buddy. Yet solo diving has long been common, particularly among underwater photographers. Experience, and incomplete statistics, don't indicate that solo diving is more dangerous than buddy diving, and some divers argue that solo diving is actually safer.

9. The Snorkel

Most of us were taught that a snorkel is mandatory gear on every dive, just like a pair of fins. But increasingly, divers are leaving the snorkel in the gear bag much of the time.
Why? They've come to the conclusion that a snorkel, when attached to your mask, is more often a hazard than a help. The long tube—dangling from its midpoint so the hook-like gizmos at the ends can wander around—is pretty effective at catching kelp, fishing line and camera straps. And, given the importance of your mask, your mask strap is about the worst place to mount it or anything else.
Many divers now save the snorkel for special occasions, like a long surface swim from their entry point to the dive site, and carry it in a pocket or strapped to their body.

10. The Dive Computer

The dive computer is probably the most important safety advance in the sport. Much more important than a snorkel, and arguably more important than an octopus, a dive computer may well be considered mandatory equipment before long. SDI already incorporates dive computers into student training from the outset. "Virtually all divers now use dive computers to make diving safer and more enjoyable. Why not establish that practice from the beginning?" says CEO Bret Gilliam. "Dive tables have simply been supplanted by advances in technology."

more on http://www.scubadiving.com/training/basic-skills/10-new-rules-scuba-diving?cmpid=obinsite

Death in the Shallows


Lesson ;

Jolie kept hoping things would get better. She had been certified a year earlier, but had been in the water only once since then. Her first dive of the day had been shaky, but she got through it. She just couldn’t get the hang of her buoyancy, and felt like she was either banging off the bottom or floating to the surface. During the surface interval, her buddy told her she just needed practice and it would get better. She kept reminding herself to relax and breathe slowly and easily.

During second dive, She was uncomfortable on the surface, trying to remember everything her buddy had told her and the lessons she had learned in class a year before. As soon as the water closed over her head, she began breathing quickly. Her buddy said later that it looked like a constant stream of air bubbles coming out of her regulator. She descended quickly and hit the rocky bottom on her knees. A group of students had just cleared the area and silt had been stirred up, reducing visibility to less than normal. Jolie stayed on her knees for a moment. She took the regulator out of her mouth and began scrambling for the disconnected inflator so she could add air into her BCD. She never found it. Her panic escalated. The only thought that reached her mind was that she needed to be on the -surface. Air.

Jolie’s buddy grabbed her -alternate air-source regulator and tried to give it to her. When she refused it, he tried to give her his own, but she refused it as well. Without warning, she bolted for the surface. Resuscitation efforts on the beach and at a nearby hospital were unsuccessful.

ANALYSIS

This is a classic case of panic leading to a dive fatality. Jolie wasn’t thinking clearly in the water. She took out her regulator before she found her inflator hose. Just those few seconds without an air supply were enough to tip her over the edge.

There is very little you can do for someone in a panic state, aside from removing them from the situation and allowing them time to calm down. This is extremely difficult and dangerous underwater. But while the panic ultimately killed Jolie, the triggers on the dive caused the panic in the first place.
Jolie had latent problems with claustrophobia. Struggling with her buoyancy got her agitated to the point that she wasn’t thinking clearly. A root cause of this issue was the disconnected low-pressure inflator. She entered the water on the second dive with the same problems, now even more agitated.

 An ascent from 10 feet was more than enough of a pressure change to cause a lung overexpansion injury and cause an arterial gas embolism, or AGE. This causes strokelike symptoms as a large air bubble is introduced to the brain, cutting off blood supply. It can also cause death rapidly. This is the reason scuba divers are trained to never hold their breath.

Lessons for Life

1 Don’t make dives you aren’t comfortable making. Don’t allow peer pressure to goad you into a dive you aren’t ready for.

2 If you feel panicked or have trouble catching your breath underwater, stop on the bottom or hold onto something stable and attempt to relax. Wait for your breathing to settle before you attempt to swim on. If that fails, abort the dive.

3 Be properly equipped for the dives you are making. Making do with improper equipment is unsafe.

4 Seek additional training and experience in a situation supervised by a dive instructor.
Eric Douglas co-authored the book Scuba Diving Safety, and has written a series of dive-adventure novels and short stories. Check out his website, booksbyeric.com.

Scuba Gear Care and Maintenance Tips


Take Good Care of Your Scuba Gear

Whether you've only seen a scuba diver in action or you’re already a diver yourself, you know that diving is an equipment intensive activity.
Keep your scuba gear in tip top shapeTo protect your scuba gear (and yourself given that scuba equipment is essentially life-support equipment) it’s important to care for it correctly. Most scuba gear comes with instructional manuals describing manufacturer recommendations for care and maintenance, but here are some general suggestions to help keep your scuba gear in tip top shape:
  • One good thing about scuba gear is that because it’s waterproof, you can wash it. In fact, all scuba gear should be rinsed in clean, fresh water after every dive. Then, it should be dried before storing it in a cool, dry place out of direct sunlight.
  • Remember to dry and firmly replace the regulator’s dust cap before rinsing the regulator to avoid any water entering the first stage. Ideally, rinse the regulator while it is still attached to the scuba tank and pressurized. That way no water will enter at all.
  • Have your scuba gear and equipment serviced regularlyUse clips and other attachments to keep all hoses and gauges close to your body while scuba diving.  This prevents them from dragging across sharp rocks or coral. This also keeps them from or getting snagged or dirty.
  • Handle scuba tanks with care. They are heavy and you shouldn’t leave them standing up unattended - they caln fall over and damage the valve or nearby toes.
  • You should rinse both the inside and outside of your BCD. Make sure to drain the water, then always store your BCD partially inflated.
  • Regularly inspect your mask strap, fin straps, snorkel and regulator mouthpieces and hoses for any sign of wear and tear. Sunlight, stretching and teeth easily damage these items so you might need to replace them sooner than expected.
  • After rinsing your wetsuit, hang it up to dry inside out on a wide hanger. Handle your scuba gear with care
  • Consider completing the PADI Equipment Specialist course to learn more about caring for your scuba gear
Put together a spare parts kit with the most commonly broken, lost or worn out items:
Fin and mask straps
  • O-rings
  • Snorkel keeper
  • Silicone grease
  • Quick release buckles
  • Pliers, screwdrivers, adjustable wrench, Allen wrench and pocket knife