The Breath Test

The Test Team puts the Poseidon Cyklon 5000 regulator through its paces. Steve Warren reports.

The Cyklon 5000 has a reputation as a rugged workhorse of a regulator, generally used by men and favoured by technical divers. This reputation is a little unfair because the regulator is actually a general purpose, mainstream regulator. It’s just that it has certain features that make it advantageous to technical divers.

The Cyklon has a side-mounted second stage – the inhalation/exhaust valve and purge are to one side, rather than in front as with a lot of regulators. This means that you can put the reg in your mouth ‘upside down’ or the right way up, without any problems. It also means that the hose can go over either shoulder. This is what makes the Poseidon regulator popular with cave and technical divers, who have found that their side-mounted cylinders and stage decompression cylinders are more easily configured with left-handed regulators – this regulator gives them the option.

It is quite a simple second stage, and it features a much longer lever (visible through the mouthpiece) than conventional second stages, which, in theory, makes breathing in easier. The lever is linked to the diaphragm at one end and the inlet valve next to the hose at the other. Inhalation causes the diaphragm to cave in, opening the valve to admit air. A venturi (a tube with a constriction that controls airflow) takes over once the valve has been ‘cracked’ open by the initial inhalation, which also helps to ease the effort of breathing.

The first stage is rated for use with pressures up to 300 Bar (4500PSI). This requires a DIN (Deutsche Industrie Normen) screw-in fitting rather than the more usual (in the UK anyway) clamp-shaped fitting (or ‘A’ clamp). DIN connections are regarded as safer because the O-ring is secured inside the first stage, making it more difficult to blow. If the O-ring does extrude it will at least slow air loss. Because the regulator is held in place by 5 (up to 200 Bar) or 8 threads (up to 300 Bar), it is very secure. For divers working in overhead environments, where there is every chance of the first stage colliding with ice, rock or wreckage, the DIN connector has been a long-time favourite. But the regulator is also useful for divers who do a lot of travelling – the regulators are supplied with a DIN connector and a clamp adaptor which can be screwed over the DIN connector. This means a Poseidon can be used anywhere in the world without buying extra tank adaptors. There are four low-pressure ports (LP) and two high-pressure (HP) outlets, and the first stage operates at 10.5 bar. This is higher than most other first stages and fitting another brand of octopus may cause it to free-flow. Poseidon recommends using another 5000 to be safe. Poseidons are not officially recommended for Nitrox use, but since they have suitable O-rings and no silicone, many divers do use them with mixes up to 40 per cent without


Our test team made five official test dives with the regulator, off the coast of Gibraltar, but we also drew on past experience we had of using the regulators in the Red Sea and in the chilly waters off the west coast of Canada, in Vancouver. The regulator was also bench tested by ANSTI in Southampton on their breathing machine.

The Cyklon 5000 fared badly in another magazine’s test report last year. It failed to provide sufficient air at 50m to meet the EN250 standard. Poseidon was trying a new spring in the first stage and this, according to the company, resulted in some regulators failing this test. This spring has now been replaced and performance increased to exceed the EN standard as demonstrated by the latest ANSTI figures (see box on previous page).

On our test, each diver set up their Poseidon to suit themselves, each attaching a pressure gauge and one or two other hoses depending on whether they dived with wet or drysuits. UWI also supplied us with octopus rigs. There’s plenty of room for hose protectors and the choice of two HP ports set at 90 degrees allows a pressure gauge to be used left- or right-handed as preferred. LP and HP ports are different sizes to reduce the risk of the wrong hose going into the wrong outlet. Clamp adaptors were used with the cylinders.

Score: 85 per cent.

Mouthpiece comfort

The mouthpiece is unusually wide, making most other mouthpieces unusable, so it is wise to carry a spare. Any regulator mouthpiece has a huge influence on the comfort of a dive, especially when doing long and repetitive diving. One of the test team made several dives a day in the Red Sea, with durations of up to two and a half hours. In Gibraltar, two to three dives of up to an hour were more common. Andrew Bell, one of the team, noted that the mouthpiece was ‘a bit on the big side’, while another member, Jeff Logan, swapped the mouthpiece for a smaller one that he found more comfortable (not a Poseidon).

Score: 65 per cent.

Primary hose

Along with second-stage weight and mouthpiece design and size, the delivery hose can also be a cause of discomfort. A rigid hose can force the second stage into an uncomfortable position and make the diver use his jaw muscles to counteract it. Along with causing jaw strain, the mouthpiece riding up can disturb the lower edge of the mask skirt, causing leakage. The Cyklon proved to be very comfortable with a supple 70cm hose. ‘Plenty of head movement’ noted Bell.

Score: 75 per cent.


Though sharing a primary second stage is going out of fashion, we asked testers to give it a try. Again, a short hose can make this difficult but the Cyklon scored well. The octopus hose length is 90cm.

Score: 85 per cent.

Purge button

The location of the side purge button makes the Cyklon easy to control, even when wearing thick gloves. The body of the valve is easy to grasp securely while leaving the purge easily accessible to either diver. In normal use, all the team found the Cyklon very easy to clear by either purging or exhaling.

Score: 85 per cent.


Three of the team were taking photographs using housed cameras, where getting your eye close to the view finder is the name of the game. Bulky second stages can interfere, making view finding difficult. The side exhaust was also appreciated.

Score: 72 per cent.


Our team inadvertently hit a very strong current that churned the Gibraltar sea-bed to mud at about 25m. For 15 minutes Jeff Logan and Andrew Bell fought this current, sometimes finning along the sand, sometimes inching hand over hand along old communication cables. This dive placed enormous strain upon the divers and of course upon the Cyklons they were using. Though the Poseidons were used at depths of about 45m on other occasions, this ‘forced march’, as it was described by one person, really tested the valves.

Score for ease of breathing to 40m:

75 per cent.

• The regulator is supplied with bag, clamp adaptor and Allen key, and retails for £305 (£445 with an octopus). Contact UWI Circle on 01420 544422.

Meet the team

Andrew Bell

An experienced diver who has worked as a film-maker in various locations around the world. He has written for Dive International on his encounters with the rarely seen and little understood six gill shark.

Jeff Logan

Has clocked up nearly 150 dives since learning to dive in 1996. He and wife Alexandra have dived in the UK, Gozo, Red Sea and Indian Ocean. Joining our Coral Queen test team in 1997 as relative neophytes, they have gone on to become regular testers and hard divers with deep, cavern and decompression diving under their belts.

Sid Thaker

An underwater photographer whose work has been featured in Dive International’s Up and Coming pages. In 1998 he spent a week aboard the Coral Queen during a private charter for photographers organised around the filming needs of cameraman Peter Scoones.

Steve Warren

Has organised Dive International’s equipment tests for the past three years and has been a regular contributor to the magazine. Is a BSAC and PADI instructor and used to be training officer of the Gibraltar Sub-Aqua Club.

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