John Bantin looks at a new piece of equipment which enables conscientious dive shop owners to make sure they are selling clean air.
Every diver should be aware of the hazards associated with a 'bad fill', but sometimes it's hard to identify a problem. Sometimes the problem can be fatal. The effects of impurities are heightened with the increasing pressure of the air breathed at depth.
The Factair F1850 Safe-Air Tester is a portable machine which uses either Draeger or Gastec air testing tubes to monitor oxygen percentages, levels of carbon monoxide, carbon dioxide, water, and any oil which may be present in air supplied either from a high-pressure air-line or from a scuba cylinder.
We don't normally test'trade' items in these pages, and this unit is not intended for individual divers - its price (around 1300) prohibits that. However, a conscientious dive-shop proprietor will certainly want to know that he's supplying air which is non-hazardous to his valuable customers. In the event of a query, he is well placed if he is able to accurately analyse the remnants of a suspect fill.
It's dive-shop proprietors who will be most interested in obtaining their own machine, using ready air-analysis as a unique selling proposition. Who knows, we might even see machines proudly displayed in stores as evidence that the air supplied is properly tested!
Dorset trading standards officers are already making regular checks on dive-shops in their area, to ensure that the air supplied is up to breathing-air standards.
The relevant British Standard 4275 and DIN3188 is now being superseded by the new European Standard PREN 12021. This allows a maximum oil content of 0.5mg/m3, 50mg/m3 of water with cylinders filled to 200bar (30mg/m3 to 300bar), carbon monoxide to a maximum of 5 parts per million (ppm)and carbon dioxide to 500 ppm.
The Factair machine is either mains or rechargable battery operated.
Deciding it would be pointless to test a fill where the compressor filters had been changed immediately prior to my visit - or a cylinder which might have been part-filled elsewhere - I visited several dive-shops in the home counties, without warning. Each owner was confident that his air would be up to standard and allowed me to test a typical cylinder of air taken at random from their hire or school stock.
Connecting the machine to the sample cylinder via its air pressure reduction valve (A-clamp or DIN fitting), air is allowed to blow through for a predetermined 'purge' period. This ensures no residual contaminants are left from a previous test.
The four relevant Draeger test tubes are then prepared by snipping off both ends to allow the passage of gas, and they are then inserted in the appropriately marked gland foreach test sample. Hitting the test button, four lights indicate that each tube has the required flow of air through it, and each light extinguishes as the test tube becomes ready for examination.
The tubes are read against the scales engraved on them. Oxygen levels are read directly from the digital display on the machine.
The owner of every dive-shop enthusiastically awaited the results. Each was impressed with the machine - if not always with its price - as it proved a simple way to check on an important product.
So what of the results of the air testing at my four guinea pig dive-shops?
These premises were all positioned in urban areas, and I noted a slightly lower percentage of oxygen than at my home in the green-belt outside London. This amounted to around half a percent and really is of no consequence provided the deficit was not being made up with some other more noxious gas!
Surprisingly, despite the presence of the heavy traffic found in towns, none of the tests revealed any carbon monoxide. However, high levels of carbon dioxide were revealed - in one case right up to the limit of the European Standard of 500mg/m3. Why this was I do not know.
No traces of oil were encountered, but since three of the shops were using synthetic oil in their compressors, it was difficult to detect anyway. (Incidently, to my knowledge, no one really knows yet what are the safe levels of chemicals present in these synthetic oils since no suitable research seems to have been done.)
One dive-shop proprietor offered the information that the only complaint about his air he ever received was that his air was too dry. As if to confirm it, the tester revealed no trace of humidity whatsoever. Not so at the other shops, which provided air samples with between 25mg/m3 and a whopping (and unacceptable) 100mg/m3 of water in one particular 200bar cylinder. The reasons for this are being investigated by the dive shop concerned.
Some of you will be sure to ask which shops I visited. I must stress that I was testing the Factair test machine, not the dive shops!
The first diving computer (the Nemesis Nitrox) from the American manufacturer Cochran, which I reviewed, was so complex that I thought I deserved an honorary degree just for reading the instruction manual! The converse can be said of the Cochran Captain. It's simplicity itself.
It's a compact unit suitable for mounting in either a wrist pod or console unit. When first fired up (by wetting the two metal contacts) it goes into self-diagnostic mode and then displays current air temperature and altitude (in 1000ft increments).
Once you submerge, it indicates remaining no-stop time, ceiling depth, current depth (to a maximum of 75m) and elapsed dive time.
It's really a no-stop diving computer, so once it's time to ascend a useful five-segment bar graph indicates the ascent rate. This varies from less than 3m/min. to 20m/min. Any faster and it starts flashing. At the end of last year, there was some adverse publicity in the UK national press against decompression tables. I believe the single most important safety aspect associated with using a dive computer is its ability to measure the ascent rate. Without this electronic advantage, can one really be sure of how quickly or slowly one ascends?
Should the diver overstay the decompression limit, the Captain will display decompression stops in 3m increments. The time at each stop is also displayed. Hence, although it's intended to be a no-stop computer, it can be used as a full information deco-stop instrument. I wasn't able to ascertain which algorithm is used, but in our side-by-side computer comparison it didn't seem so different from the other American-made computers of similar dimensions, and if anything, it was a little more cautious.
Despite an unfamiliar display layout, I soon found it quite easy to read and understand underwater. In surface mode, it displays the current surface interval, the previous dive's maximum depth and dive time, and alternates to show current air temperature and safe time to fly. After one minute of this it switches to dive-planning mode, where it scrolls through predicted no-stop times and depths.
At the end of each dive-planning scrolling sequence, it goes into log-book mode, where the user will be able to review the last eight dives made without a full desaturation interval.
The information includes dive depth and time and the surface interval between dives, together with the fastest rate of ascent made.
Since all this information is in sequence, you have to be very patient if you miss anything because you have to go through everything before it all comes round again. This is the sacrifice one must make to have the simplicity of a two-contact machine. Four-contact systems are more of a pleasure to use on the surface.
Cochran Undersea Technology prides itself in its relations with its end-users, and maintains a staff of fully qualified divers to answer queries. They're only a fax or phone call away during office hours (allowing for the Texas time difference).
What's the time? It's a question that's almost embarrassing to answer when you're wearing the new Citizen Promaster Aqualand watch.
What' s the time in England? What's the temperature? How deep did you go? Can you time this to the nearest hundredth of a second? Can you wake me when your alarm goes? Will you tell me if we go deeper than? Will you make sure we don't ascend faster than? These are the questions that this extremely chunky piece of masculine jewellery begs to be asked. I wore the latest Promaster Aqualand watch in a rather self-conscious way during a recent dive trip abroad. It looked a little incongruous on my skinny wrist. I was rather concerned it might attract attention from other divers. You know the type: those who go on about 'lobbies' and 'flatty bashing'. It's certainly not as discreet as my more usual example of fine Swiss clockwork. The Aqualand is Japanese and is driven by quartz electronics.
Firstly, it has an analogue face (that's a big hand and a little hand!). You can set the hands by winding out a watertight crown and fiddling. Then there is the mode button. It's one of three buttons positioned around the chassis on the watch. This allows you to select either time, alarm setting, chronographic, dive logbook, or diving modes.
In time mode, the digital displays show the time and elapsed seconds. You can adjust the analogue setting (the hands) to local time and keep the digital setting at GMT, for instance, if you so wish. In this mode you can use two other buttons to check the date, the year, find out the temperature, or adjust the display.
The digital displays have several alternative functions. In alarm mode, you can set the watch to sound an alarm at a predetermined time. In chronograph mode, you can use it as a stopwatch. In logbook mode, I found I could recall the maximum depth and time of the last dive - plus the start and finishing times.
On the occasion I found myself diving without my mask with its prescription lenses, I found the underwater alarms very useful. I could set an alarm for a predetermined maximum depth, which reminded me to squint at my computer.
This alarm can be set to repeat up to five times a minute. There's a preset dive-time alarm and there's an alarm if your ascent rate beats 9m/minute.
If all this sounds rather noisy, I can assure you that the alarms are quite discreet: almost inaudible at the moment of exhaling large quantities of noisy bubbles.
Under water (it's rated to 200m), the watch automatically enters diving mode and displays depth and elapsed time. Every minute, the water temperature is displayed as well. You can check water temperature at will by pressing one of the watch's buttons.
If you decide not to trust the electronics, you can revert to using the hands in conjunction with the uni-directional bezel ring, which you must set immediately prior to submerging. This watch makes no computations. It is merely a measuring device. It is not a substitute for decompression tables like the BSAC '88 or PADI RDP, or a full-blown diving computer. But you'll have lots of fun with it, and it makes a good conversation piece during long journeys in aircraft!
As I grew older my arms seemed to become shorter. It reached the point where I could no longer hold a newspaper far enough away to read more than the headlines. Under water, I started to rely too heavily on the audible signals from my computer.
Nearly every mask manufacturer accommodates those who need negative-rated lenses for short-sightedness. But for those suffering the ravages of time like me (presbyopia) and long sightedness (hyperopia) there seemed fewer options. I experimented with a little meniscus lens glued to the inside of one mask glass. This was fine for squinting at my computer, but certainly no good for the more esoteric needs of underwater photography.
I found the apparent lack of interest from the trade rather strange. Surely, I thought, we 'oldies', with children off our hands and mortgages paid off, were an important target group in the leisure market? Why couldn't I buy a plus dioptre corrected mask as easily as I was able to buy some cheap 'Readyspecs' in the local chemists?
I stumbled across Mark Kass, a diving instructor, dive-shop proprietor, and consultant dispensing optician. He explained the technical problems which made the successful manufacturing of twin lens mask direct replacement lenses (plus dioptre) impractical. Because masks must have a minimum edge thickness, for safety reasons, they would often end up with lenses so thick their wearers wouldn't need a weightbelt! Vision would also be highly distorted at the edges, cutting peripheral vision. Then there's the question of appearances. No one wants to look like they're looking at the world through the bottom of two milk bottles!
Plastic lenses, too, have problems. They scratch easily and are not regarded as safe under EC rulings. However, technology marches on, and Mark Kass and his company, Seymour Clearly Opticians, can now make any single vision lens to any prescription, and most bi-focal prescriptions.
The company uses the plano tempered-glass blanks already in the mask, and bonds the lenses to the inside of the mask glass. As a consequence, it can now make bifocal or single vision minus or plus prescriptions for any single lens, twin lens, or multi-lens mask, where the original lens is removable and replaceable. Varifocals have proved unsuccessful because of blurring at the edges of vision.
I ordered a new mask by phone and received it complete with the lenses installed only 10 working days later.
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