Jack Ingle is the BSACs Technical Diving Adviser. He is a BSAC National Instructor, an IANTD Technical Instructor, a TDI Tri-mix instructor and co-author of NSAC nitrox courses.
I have recently started twinset (twin 10 litres) diving without any real problems, aside from the fact I am unable to reach the manifold or cylinder valves when wearing my rig with my Otter drysuit. Do you have any suggestions about ways I can reach the manifold I have tried mounting the twins on the BC (DiveRite Rec Wings) with the available mounting holes in different ways but to no avail. I was wondering if there are any recommended contortions I can try

This is not the first time I have had this question and I spend much time on technical diving courses teaching divers how to get over this problem. The first thing you must understand is that you must be able to get to the valves. Diving a manifolded twinset could potentially be lethal if you cannot carry out the shutdowns efficiently, quickly and without help from your buddy.
A free-flow will exhaust your gas supply in a very short space of time, and Sods Law dictates that the day this happens you will probably have lost your buddy as well.
Now lets look at solving the problem. Ten litre cylinders are quite short, and when mounted in your wing will be quite a way down your back, making access to the valves difficult. Twelve litre cylinders are that much taller and do not generally give you this problem.
You can try to raise the cylinders higher in the cylinder-twinning bands, which will bring the valves higher up, making access easier. You must not raise the cylinders too high, as this will make them top-heavy and cause you to nose-dive when trying to swim horizontally.
You also say that you cannot reach the valves when wearing your drysuit. I dont know which Otter suit you are using but the companys membrane suits are usually very supple and allow good flexibility. If the suit is a little small, this will reduce arm movement and make the job difficult. The suit must allow you to reach down your back without any restriction to your natural movement.
If the suit does restrict your movement, a quick call to Otter to discuss a couple of modifications should solve the problem John and Paul at Otter are very good and will always help you out.
The simplest way to get to the isolator valve in the centre of the manifold is to fit a remote, otherwise known as a slob knob. This is just an extension to the isolator and I wear mine on my left-hand waistbelt D-ring. It makes access far easier than having to put your hand over your head.
Some divers who really cannot reach the cylinder valves fit remotes to these as well. In that way all valves can be accessed from the divers front, and shutdowns are very simple.
I find that I can reach all cylinder valves by reaching backwards, and there is a technique to doing this. Try it in a swimming pool, while wearing your drysuit.
First, put your hands directly behind your head. You will probably find out that your hands will not be that close to the valves. Now try it again, but first stretch out your arms directly in front of you as far as you can get them. You should feel a pulling in your shoulders.
Now raise your arms directly above your head, still stretching, and you will feel your back extending slightly as well. Slowly bring your arms down behind your head and you will find that your hands will touch the manifold.
I carry out this flexibility exercise before diving to warm up my joints and loosen me up. This type of exercising needs to be continuous and makes you far more supple over a period of time. Add it into a regular training programme.
Getting hold of gases
I am planning a diving trip for myself and friends in the south-west of England, to carry out some technical dives. One problem we face is getting access to the gases we need, trimix and nitrox. Do you have any suggestions

Pete Barnes
This is a problem I face all the time, as I run expeditions around the UK and abroad. It is difficult to transport gases, compressors and blending systems but some destinations demand it as there may not be the facilities you require, such as a local dive shop which pumps gas. More importantly, if you do plan to pump your own gas, make sure you have the correct training in blending nitrox and trimix, as there are potential dangers involved.
The simple answer, of course, is to find a gas-blending centre close to where you are planning to dive. I recently carried out a diving expedition on the South Coast and we needed to refill the cylinders in the evenings ready for the next day. I made a few enquiries and found a dive shop in Selsey, West Sussex called Ocean View.
A quick telephone conversation with the owner, Dennis, to explain our dilemma and he immediately solved the problem. He offered to stay open late and even return to the shop one evening at 9pm just to fill our cylinders. It was also very useful for those extra bits of kit that had been lost or broken during the expedition - a ready-made spare-parts centre.
These people could not have been more helpful, but I have found that to be the norm when this problem has occurred before. My suggestion is to start phoning around the dive shops in the area you are visiting and get talking to the owners.
Air obsession - was I narked
I recently carried out a dive to 45m and can only describe my feelings as very strange. I felt concerned about my air supply throughout the dive and found myself constantly checking the gauge. There was no problem with my equipment or the amount of air I had. My buddy said it was narcosis, but I have never had it like that before. Could this be the case
Simon Dear

I agree with your buddy, it certainly sounds like a severe narcosis hit to me. Remember, nitrogen narcosis symptoms are not just I feel bad or I feel good. There are many other manifestations.
Lets nail down some facts about narcosis. Many tests have been carried out over the years by scientists, physiologists and the military. In recreational diver training we state that narcosis starts at about 30m, though I have seen many divers showing signs of it far shallower than that. I know a few divers who look decidedly dodgy walking over Waterloo Bridge.
Narcosis affects all divers in different ways and at various depths. The same diver can be affected differently at the same depth on different days. Royal Navy tests found that severely narked divers gave hand signals continuously under water but on the surface could not remember giving them - or indeed anything else that occurred on the dive.
I have also seen technical divers surfacing and stating that they could remember nothing of a dive.
You were checking your contents gauge constantly, and this is known as analytical narrowing. You fixate on one task and cannot easily cope with anything else. To find out if it was narcosis, ask yourself whether the symptoms disappeared as you got into shallower water.
Narcosis is a serious problem with deep air diving but there are several steps you can take. First, know your own limits and stay within them. Monitor the onset of symptoms and be aware of them in yourself and your buddy.
Minor symptoms of light-headedness can soon lead to severe confusion and panic, so ascend slightly before things start to go wrong. Avoid alcohol or drugs before diving, as this increases the effects of narcosis. Stay warm, use good underwater lights and be as relaxed as possible during the dive.
Descend slowly on deep dives, as rapid compression increases the effects of narcosis. Dont work hard under water, as this increases the CO2 levels and in turn increases your potential for narcosis. CO2 toxicity can cause blackout under water, and I dont need to explain what would happen to you then.
If you really want to reduce the risk of narcosis, dont use air on deep dives. This is one of the reasons we use trimix for deep diving - by replacing a lot of the nitrogen with helium, we get rid of many such problems.
Above: Easy enough to reach the central isolator valve this way round, but are you supple enough to reach it when its behind your neck Below left: Jack Ingle found the Ocean View shop at Selsey very accommodating when he needed gases blended for the next days diving