Wrong gases?

[Zippsy]

The "breaking" above I believe is the un-edited first draft. The edited story that made it in print and is on the newspapers website now is:

Trainee diver's death remains a mystery

A TRAINEE diver, just one dive away from qualifying as an open-water diver in February last year, never finished his quest.

A scuba tank filled with an exceptionally high level of carbon monoxide ended it for Mr Sue Qing Wen off Pulau Hantu. The 20-year-old sank out of the dive crew's sight and drowned; his body was found three days later, the tank still strapped on.

Lab tests found the tank to contain 785 parts per million (ppm) of carbon monoxide and 12.3 ppm of hydrogen sulphide - both toxic. The compressed air in a normal scuba tank should contain 80 per cent nitrogen and 20 per cent oxygen.

Nobody at the inquiry into his death could explain how so much of these poisonous gases got into his tank; neither could it be determined how inhaling them could have affected him.

State Coroner Victor Yeo thus recorded an open verdict.

The Health Sciences Authority's forensic scientist Chia Poh Ling said the high level of carbon monoxide in the tank could have come either from a contaminated air supply or the tank having been filled where there was a high level of the gas. Another tank taken off the boat was found filled with the expected 20.7 per cent of oxygen, 55 ppm of carbon monoxide and 1.7 ppm of hydrogen sulphide.

The manager of Dolphin Dive & Adventures Francis Yeo, 29, testified that when he filled up the 24 tanks a day before the dive, he did it by the book. He said he also turned off the boat's engine and placed the air-intake valve upwind of the compressor engine so exhaust would not be sucked into the tank.

Associate Professor Philip Eng of the Department of Respiratory Medicine at the Singapore General Hospital said too much carbon monoxide causes dizziness and nausea; fits set in within 45 minutes, and unconsciousness, in two hours.

Exposure should not exceed more than 35 ppm of the gas over eight hours.

On Feb 17, Mr Sue and five other dive students headed out to Pulau Hantu with several others for their final dive assessment following theory lessons and a practice session in a pool.

The first two dives were uneventful. Before the third and final dive, the trainees changed tanks.

Mr Sue was paired with fellow trainee Mohamed Fairus Jumali, 35. They entered the water with divemaster Gerald Chew Tiau Chin, 27, descending vertically by holding onto a line tethered to the seabed.

When they had gone down 8m, the trio paused to make way for another trainee going up. This was when Mr Chew and Mr Fairus lost sight of Mr Sue. Mr Chew looked for him on the sea bed to no avail.

He resurfaced and alerted Dolphin Dive employee Joanne Sim Hui Jun, 28. It was she who saw Mr Sue surface a distance away, waving and without his breathing apparatus.

She signalled to him to put it back on and inflate his buoyancy compensator device, a vest worn by divers which can be inflated or deflated to control buoyancy.

A lifebuoy thrown towards Mr Sue fell short of him. Ms Sim said Mr Sue, then conscious, sank into the water amid strong currents.

The family's lawyer Simon Tan, said Mr Sue's parents felt that the circumstances of his death are no clearer now and want to see justice done. They are considering commencing legal action against the relevant parties.

Mr Tan said that on the day of the incident, the family waited for Mr Sue to join them for their Chinese New Year reunion dinner.

Instead, they got a visit from the police after 8pm bearing the news that he had gone missing.

 

[Zippsy]

a couple of points: Yes, you would need a shovel to go deeper than 15m anywhere near where they teach OW around Pulau Hantu. Usually, it's closer to 10m deep. It is very possible though that the anchor line was 35m and they were heading to the end of it with 20m or so laying on the bottom.

Yes, I bet he was overweighted too. It's a fairly common "shortcut" taken by too many instructors here. Since he made it back to the surface, he should have survived IMHO. Disoriented from the CO and H2S, there is only a little chance that a new diver would have thought to dump his weights and inflated his BCD but he should have been able to stay afloat for longer unless he was overweighted. We don't wear drysuits or 5mm here. I'd bet he had a 3mm shortie at best.

Viz was certainly less than 3m. It's a rare day when it's better than that.

Light reading on H2S: http://www.wccoff.org/hydrogen sulfide gas fact sheet.pdf Sounds like it's not so fun to breathe.

Finally, the reporting in Singapore has come a long way since it was just the mouthpiece of the government. They have a sports section now. They still make at least 5 mistakes every time they write a scuba story though. If not for the story usually about a death, it would be comical.

 

[wilde100]

Zippsy seems to be familiar with Hantu... Can anyone suggest what the instructor should have done?

I'm curious if more could have been done to help the student given a site known for its strong currents and poor viz.

 

[ScubaSteve]

Zippsy seems to be familiar with Hantu... Can anyone suggest what the instructor should have done?

I'm curious if more could have been done to help the student given a site known for its strong currents and poor viz.

My first suggestion would be to not allow a student to get away from you. If he surfaced far enough away that nobody could reach him then that means the instructor and crew failed him. We pay the instructor to make sure that that sort of thing does not happen. "Smelly Stuff" happens, but to lose a student is unacceptable IMHO.

 

[DandyDon]

I'm bothered by this excerpt from the latest version: "Another tank taken off the boat was found filled with the expected 20.7 per cent of oxygen, 55 ppm of carbon monoxide and 1.7 ppm of hydrogen sulphide."

Wrong Wrong Wrong! The common scuba industry maximum is 10 ppm CO, and expected should be less than 1 ppm. Can't do anything about journalism but I thot the facts may be interesting here.

The Associate Professor Philip Eng of the Department of Respiratory Medicine was probly being quoted out of context.

I have no idea what the maximum allowed or average expected of H2S might be?

 

[theunraveler]

I remember this case, the week before I was there on a sat morning doing leisure dive. The water visibility was so bad you can stretch ur hand out and not see your elbow. My buddy and I in the end we just end up holding each other's hand because it was impossible not to lose sight of each other under these condition.

In the end we just swam around under water, holding each other's hand and trying to make the best of a bad situation till it was time to surface. Even though there was a 2nd dive available I didnt go for it because it was god awful.

 

[Zippsy]

a half hour boat ride from one of the largest container ports in the world, Hantu is never going to compare to Sipadan or Cayman but if you live in the great city of Singapore, for $50 you can do two dives be back in time for lunch. Also, it you sat out the second dive, you missed some decent stuff. Pulau Hantu . Then again, you may also miss the CO and H2S too.

 

[Zippsy]

DD, he probably expected 55ppm of CO because that is the pollution we have over here from our cars and the factories in nearby Indonesia. I am only partially kidding but I bet he was mis-quoted too.

Wilde, I was taught OW and Rescue at Hantu and I did my IDC there. What should have the instructor done? I'll get hit for saying this but 1) not dive there while currents are strong (which means checking tide charts and/or moving the boat; 2) kept closer watch over the students (DM's in the water); 3) train them better in the pool (more than one 3 hour class); and 4) don't overweight the student.

When I did my OW there, two minutes into my first dive, my buddy's waving arms knocked off my mask and reg. Because of the excellent training I got (including 4 pool sessions rather than the one that this guy almost certainly got), I calmly found both and replaced them in time to see the passing turtle. Competition in Singapore for students has meant that the course cost has come down steadily over the years just as the cost of living has gone up considerably. What do you think gets cut? Sad, ain't it.

 

[widget]

Hmm,as in most fatalities its not one single thing, but the compounding of many small mishaps that leads to the tragedy.

Here, we have a known case of contaminated air, the instructor lost contact with the student, it appears he may have been overweighted, strong currents would lead the diver to overexerting himself, he was certainly disorientated at best or downright ill at worse on surfacing, a life support was tossed to him but fell short (this is disgracefull) and no mention is made of any further attept to make contact with him - the copy states he was "concious and started sinking" this leads us to believe he also did not have the presense of mind to inflate his Bc or search for his demand valve.

Very distressing indeed and I would hazard, completely avoidable with better controls and air quality check systems.

 

[Ayisha]

I'm bothered by this excerpt from the latest version: "Another tank taken off the boat was found filled with the expected 20.7 per cent of oxygen, 55 ppm of carbon monoxide and 1.7 ppm of hydrogen sulphide."

Wrong Wrong Wrong! The common scuba industry maximum is 10 ppm CO, and expected should be less than 1 ppm. Can't do anything about journalism but I thot the facts may be interesting here.

I noticed that high "expected" (55 ppm) level of CO too, Don. They don't seem to realize that "expected' level is unacceptable and deadly, especially at depth.

Exposure should not exceed more than 35 ppm of the gas over eight hours.

I wasn't sure what to make of the above part either. That is apparently 35 times what should be expected for compressed air.

I also don't understand the "open verdict". Clearly the high CO and Hydrogen Sulphide were significant contributors to Mr. Wen's death.