How good are Poseidon Regulators?

Poseidon Regulators

Versatile, robust and safe. Poseidon regulators deliver the experience that all divers seek. Unrelenting performance and safety in any environment. Expect excellence.


The Poseidon company was founded in 1958 in Gothenburg, Sweden, by Dennis Österlund and Ingvar Elvström. It was the first in the world to produce a single hose regulator, the breathing apparatus used by nearly every recreational diver ever since. The original name – Aqua Sports – was changed as the company began to look at new markets for its products.

Today, Poseidon exports to almost every country in the world, bringing the ultimate in diving gear to demanding recreational divers, rescue divers and the military. Manufacturing and research have taken place at the company’s modern factory and test facility on the outskirts of Gothenburg since the mid-80s.

The history of recreational diving
Diving as we know it began with military divers breathing pure oxygen at limited depths. In the 1940s, Jacques Cousteau changed diving forever by introducing the aqualung and skin-diving, and in 1958 Poseidon instigated further dramatic progress with the launch of its revolutionary new regulator.

In the early 80s, American NASA engineer Dr Bill Stone had the idea of applying the principles used for astronauts' breathing apparatus to measure and control the amount of oxygen in a rebreather at changing depths. In 2005 Poseidon created a project team of Swedish and U.S. engineers, under the leadership of Dr. Stone and Jonas Brandt, with a mandate to develop the rebreather concept for recreational divers.

The world’s first recreational rebreather
The Poseidon MKVI is a rebreathing system designed for recreational divers. Exhaled air is purified of CO2, refreshed with a carefully measured amount of oxygen, and recirculated.

The diver breathes warm gas and since the air is retained in the breathing loop, there are no bubbles, which means that natural experience is reinforced. The Poseidon MKVI is designed, made and tested at Poseidon’s Gothenburg factory. For additional safety and quality control, each one is test-dived before sale.

The objective; design the most reliable HP valve in the world. Every engineer knows the benefits of using balls in valve arrangements, since they will never be misplaced and will always end up in their perfect position. Unfortunately, varying upstream pressures will either push the ball too forcefully into the seat or leave it insecurely loose, giving unbalanced characteristics.

By inventing the oating seat (which automatically repositions the ball) the increased upstream pressure is balanced equally with increased and counter-acting compression forces from the pressure adjustment spring, maintaining the benefits of having a perfect ball as the sealing element. The Xstream regulator is also self-balancing, which gives the same high performance irrespective of the pressure in the cylinder. When the seat is moved upwards by the high pressure, the design causes the upper pressure spring to compress and thus exactly self-balance the powers of pressure.

Xstream also has a built in anti freeze protection in its construction. TDA (Thermo Dynamic Antifreeze) ensures that the through- flowing water keeps the ice away, entirely without fluids or extra diaphragms.

Controlling the power of a massive air flow, astonishingly reaching some 2100 litres/minute is an engineering challenge. The solution to this was to obtain a precision regulation, keeping breathing pressure to within +/- 5 mm.w.c throughout the inhalation cycle, regardless of depth and demand. Called a servo-assisted valve, it works in the same way as does the power steering you may have on your car – it’s all about compensation.

Prior to diving, when you pressurize the regulator, the main blue bladder valve is inated with the interstage pressure, along with all inner volumes including the upstream side of the servo valve.
When this is done a “swoshing” sound of streaming air is heard.

The system is then activated. On inhalation, the forces from the inhalation diaphragm easily overcome the light forces to crack open or “tilt” the servovalve and in turn evacuate all inner volumes. The main blue bladder valve then collapses and in turn lets an amount of gas out, corresponding to the actual demand.

This technology ensures that the lightest possible effort can result in an almost limitless amount of gas on inhalation.

All the more astonishing is the fact that Poseidon introduced this technology to the market as far back as 1981.

The Jetstream: traditionally popular with technical divers as well as the Swedish and US navies. An easy breathe at any depth, the second stage incorporates a safety valve that allows you to continue to breathe normally in the unlikely event of abnormally high pressure air being delivered to the second stage. Approved to EN250 cold water standard.

A regulator must possess a set of functions which are unaffected by the different environments it will see during its lifetime. Examples of these functions include inhalation resistance, exhalation bubble distraction, noise and leak tightness – to name just a few. Different environments such as cylinder pressure, diving attitude, depth, temperature, gas, type of water, the diver can have an effect on these functions.

When a new regulator is released on the market, it has to pass the EN 250 test. This test represents one single environment; the manufacturer may have managed to test perhaps another hundred such situations, which is good but not necessarily enough. Only after years and years of actual use by divers around the world will the manufacturer collect all the information which can guarantee a perfect performance under all circumstances. This of course, takes time...

The Poseidon Cyklon Junior was introduced in 1958. In small steps, it has been gradually improved every year, based on both divers’ experiences and technological evolution. And so it continues.

The expression “been there – done that” applies to The Poseidon Cyklon more than to any other regulator on the market.

The objective; design the most reliable HP valve in the world. Every engineer knows the bene ts of using balls in valve arrangements, since they will never be misplaced and will always nd their perfect position. Unfortunately, varying upstream pressures will either push the ball too forcefully into the seat or leave it unsecurely loose, giving unbalanced characteristics.

By inventing the oating seat (which automatically repositions the ball) the increased upstream pressure is balanced equally with increased and counter-acting compression forces from the pressure adjustment spring, maintaining the bene ts of having a perfect ball as the sealing element. The Xstream regulator is also self-balancing, which gives the same high performance irrespective of the pressure in the cylinder. When the seat is moved upwards by the high pressure, the design causes the upper pressure spring to compress and thus exactly self-balance the powers of pressure.

Poseidon is one of few manufactures with mouthpiece regulators approved for cold water service by US Navy.

To achieve high air ow on demand, the diameter of the supply nozzle in the second stage has to be of suf cient size: however this impacts on other aspects of a regulator’s design. This nozzle is covered by a plate or “valve seat”, which ensures that gas does not escape when not in use or during exhalation. Force is required to hold the plate in place against the gas pressure – assuming that it is a downstream opening valve seat, as is the case in most conventional regulators. It is the force required to “crack open” the valve – the inhalation effort – which divers want to keep to a minimum.
As mentioned, with the nozzle diameter “set” according to physical laws, therefore the corresponding force to seal the nozzle is also predetermined. These laws mean that to make a high performing and enjoyable regulator, the given factors would result in either a huge diaphragm to obtain the necessary forces, or a high inhalation effort.
One solution that does reduce the inhalation effort is to use a sharp edge against the valve seat – this reduces the force needed to keep the valve closed. This is not satisfactory as it dramatically increases wear. Another option is to use Venturii- effects to fool the regulator diaphragm into believing that there is a greater demand due to local under-pressure zones near the diaphragm. However this too is not satisfactory as the Venturii-effect is dependent on depth and breathing pattern which means that performance will be affected by depth which is never good.
Our solution is Servo technology. It is like power steering in a car. A servo controlled valve is basically made of two valves; one very small and one bigger. The smaller controls the bigger. By having an extremely small valve, with a correspondingly small nozzle, the forces to keep it air-tight and therefore to open it are much smaller. In addition, since the force to keep the bigger valve shut comes from the interstage pressure itself and is controlled via the servovalve, it doesn’t require sharp edged seals and it can be greatly increased in respect of outlet area to achieve very high air- ow capacity.
A common misconception regarding the Jetstream servo valve is that since the servo valve is an upstream opening valve, in case of an increased interstage pressure the servo will shut, preventing the main valve from opening.
This is incorrect. The Jetstream second stage is equipped with a safety valve in case a high pressure air ow occurs. This safety valve prevents the airstream from owing out through the mouthpiece straight into your mouth. Instead, the construction will release the air into the water via the hose. In all cases it is possible to breathe from the second stage.

What is a breathing curve?
Have you ever thought of how you breathe? When you inhale and exhale you create something called a breathing curve or a loop. A breathing loop is also a way of measuring the performance of a regulator and is measured in Joules per litre (see picture). For example the total work of breathing might be 0,75J/l. The gure shown in charts is normally the sum of inhalation and exhalation with an optimized regulator in a test bench, which means it does not show if the inhalation was extremely high and exhalation extremely low or vice versa.
Some regulators rely on knobs and levers to be manually adjusted. To get optimum performance out of such a regulator as you descend or ascend is extremely hard as there are many parameters to consider. Our idea is that this should work automatically.

At Poseidon we focus on inhalation resistance as breathing out is easy for the human body. The Cyklon achieves this through overall design and the Jetstream and Xstream by servo technology. The servo valve is unaffected by depth or what pressure it has to work at, as the force required to open it is extremely low. Next time you ask about a regulator’s breathing curve ask them about inhalation resistance and if the regulator adjusts this automatically so that you don’t end up being the regulator.

Balanced  this means that the regulated pressure is independent from the upstream pressure, e.g. IP independent from cylinder pressure, or breathing pressure independent from IP. The conventional way to obtain this is to arrange the valve in such a way that the upstream pressure either: acts only on surfaces perpendicular to the opening and closing direction, thereby having no effect on opening and closing forces; or the upstream pressure leads through the valve to an opposite surface of equal area, leading to an automatic equalization (balancing) of forces in the opening and closing direction.

Either way, it leads to a more stable performance and higher regulating precision.

Upstream valve vs. downstream valve  an upstream valve opens in a direction opposite of the  ow direction which will be established when the valve opens.
A downstream opens in the same direction as the subsequent  ow. An upstream valve will seal tighter and tighter with an increasing upstream pressure, while a downstream will open when upstream pressure reaches a certain threshold pressure.
SCUBA regulators with upstream valves must have something acting as a pressure relief valve somewhere in the line, to ensure that explosions are not caused in case of an excessive pressure. Downstream valves will open spontaneously, but if used, for example, in 2nd stages, will be more prone to start free- owing under the same circumstances.

p/v loop, breathing diagram - A p/v loop is a way to visualize a regulator’s breathing performance by plotting the breathing pressure over the displaced volume. Most often, the breathing starts with an inhalation to the right at the x-axis, and the inhalation forms a graph ideally close to the x-axis. When exhalation starts, the graph plotter turns and goes back again on the positive side of the x-axis until the inhaled volume has again been exhaled. This then forms a “pressure/ volume loop”. The x-axis intersects with the y-axis exactly at the actual pressure at depth, and can be said to be the target regulator pressure. If both the inhalation and exhalation curve did not deviate from the target pressure whatsoever, we would have a perfect regulator, with no inhalation- or exhalation-resistance.

Norsok U-101  Since the EN 250 standard only states- dynamic performance testing to a maximum depth of 50m, and accordingly requires a maximum approved diving limit to 50m, it cannot be used for type approving regulators capable of more. The Norwegian Off-Shore industry has established standards similar to the EN 250 which describes testing down to 400m. This standard was accepted by the noti ed body to be used to approve the  rst ever Open Circuit SCUBA regulator to be approved for use down to 200m – the Xstream.

Unparalleled performance, there's simply no others like it.

The regulator of choice for the most formidable of divers. The XStream works with air, nitrox, trimix or 100% oxygen. Certified for use down to 200 m / 656 ft, this regulator never quits, giving it the honored place as the US Navy's, US Coastguard's and the NYPD's preferred regulator. There is no other way to put it, the Xstream has earned its name.

The Xstream features technology like non other. Taking advantage of a side purge, current-induced free flow is prevented while at the same time diverting bubbles that would otherwise obstruct the divers view. The regulator's small size keeps it out of the way while its symmetry allows use from both the left and right side.

The objective; design the most reliable 1st stage in the world. A patented ruby ball seal is automatically positioned by the floating seat which balances any upstream pressure equally with the pressure adjustment spring, maintaining the benefits of having a perfect ball as the sealing element without the risks that follow with incorrect sealing pressures. This makes the Xstream Range self-balancing, giving the same high performance, irrespective of the pressure in the cylinder.

Added to this the range has a built in anti freeze protection in its construction. The TDA (Thermo Dynamic Antifreeze) ensures that the through-flowing water keeps the ice away, entirely without fluids or extra diaphragms.

Robust, high performing, easy to use and cold water ready. The Cyklon just works. Now updated to X with the Xstream first stage and you have a regulator that will last a lifetime.

Only through years and years of use by divers around the world can a regulator truly find its limits. Poseidon's Cyklon has been put to the test for over six decades. Through continuous and gradual improvements, the Cyklon guarantees the highest performance under all circumstances.

A unique design allows use from both left and right

Reliability to an entirely new level, making it the regulator of choice for many professional divers including for example the German Navy.

Cold Water Ready
Approved to EN250 cold water standard, giving unwavering performance.

Downstream valve
A downstream 2nd stage valve ensures air will flow, no matter what.


Q: I have noticed a loud whistling noise coming from the 1st stage on my Xstream regulator, when breathing in it. What is causing this and is it dangerous?
A: A whistling noise can sometimes be heard when the Xstream first stage is pressurized or depressurized. This is due to a resonance frequency which takes place between the ball bearing and the actuating pin. This noise should however not be detectable during low flow rates such as while breathing. The noise has absolutely no effect on the regulator functionality.
In most cases, the noice can be removed by turning the actuating pin a quarter turn. Contact your nearest Poseidon service center and they can help you with this.

Q: How long is the warranty period on a new Poseidon regulator?
A: When you buy a new Poseiodon regulator, it comes with a 24 month warranty. This warranty can be extended with our Life Time Warranty program. You can read more about the terms of our Life Time Warranty program under the Register section of this page. Other products, except those that are regarded as consumables, comes with a 24 month factory warrant.

Q: How often do I need to service my Poseidon regulator?
A: It depends on how much you dive. If you dive 40 - 50 dives a year, we recommend that you service your regulator once every 24 months. If you dive more then that, you should service it once every year. Those that dive every day, should have it serviced at leat once every 6 months or so. Remember that your regulator is life support equipment, designed to keep you alive. If you don't maintain your regulator, it could cause a failure of the equipment.

Q: Can I use a Cyklon, Jetstream or Xstream Deep regulator with nitrox?
A: The Cyklon, jetstream and Xstream Deep are certified and approved with gas mixes that contains a maximum of 21% oxygen. The mentioned regulator models have Nitril o-rings and a silicon based lubricant is used. So it's not suitable for gas mixes that has higher levels of oxygen. If you intend to dive Nitrox, you should use the Xstream Duration, that is approved for gas mixes with a maximum of 99,95% oxygen.

Q: What Poseidon 2nd stages can I combine with what Poseidon Octopus?
A: You can mix Jetstream and Xstream 2nd stages/octopus on the same 1st stage, as these two 2nd stages work with the same intermediate pressure. But you can NOT mix a Jetstream or Xstream 2nd stage with a Cyklon 2nd stage/octopus. The reason is that the Cyklon 2nd stage works on a higher intermediate pressure then the Jetstream and Xstream 2nd stages. Mixing Jetstream/Xstream 2nd stages with a Cyklon 2nd stage can be dangerous!

Q: What´s the intermediate pressure on Poseidon regulators?
A: The Jetstream and Xstream regulators should be set to 8.5 bar (123 psi) intermediate pressure, at full tank pressure. The Cyklon 5000 regulator works at an intermediate pressure of 11,5 bar (166 psi) at 20 bar (290 psi) tank pressure.

Q: Can I use a standard 9/16 LP hose on my Poseidon regulator?
A: If the 1st stage you have, has an over pressure valve built in to it, or has an external over pressure valve attached to a LP port, you can use a standard 9/16 LP hose, if it fits on the 2nd stage connection. For the Jetstream and Xstream 2nd stages, there is an adaptor available, that allows you to connect a standard 9/16 LP hose to the 2nd stage.

Q: If I put a Cyklon 2nd stage on a Triton 1st stage, do I need to modify the Triton 1st stage in any way?
A: The simple answer is no. All you need to to, is to adjust the 1st stage to the correct intermediate pressure that the 2nd stage works at.

Q: Why won´t a LP hose fit in the LP port of my old Cyklon 1st stage?
A: On older Cyklon 1st stages, the standard thread size of all ports were 1/8. Today, all LP ports are 3/8 and all HP ports are 7/16 sized. If you have an older style 1st stage, there are adaptors that be used, so you can attach standard sized hoses to your 1st stage.
Male 1/8 --> female 3/8 thread (Article number 2415)
Male 1/8 --> female 7/16 thread (Article number 2910)

Q: What 1st stages can I use the Atmosphere Full Face Mask with?
A: The Atmosphere FFM is CE approved togeather with the Xstream 1st stage and it's with this 1st stage the mask performs best. If you intend to use the Atmosphere FFM with an other 1st stage, make sure that the correct intermediate pressure is used.

Q: My Atmosphere FFM is vibrating when I breath through it. How can I resolve this?
A: Most likely, you have your FFM connected to a non-Xstream 1st stage or the intermediate pressure on your 1st stage is not correct for the Atmosphere FFM.

Q: Can I put a standard Jetstream 2nd stage on a Atmosphere FFM?
A: The Jetstream PP (the Atmosphere´s 2nd stage) is a modified Jetstream 2nd stage which is constructed to work in conjunction with over-pressure and hold low CO2 levels inside the face mask. Thus you can NOT put a standard jetstream 2nd stage on an Atmosphere FFM. Doing that can cause injury or death.

Q: How can I check if my Besea W50 wing was one of the re-called wings?
A: If you open the zipper on the outer wing bladder, and look at the inner bladder, you will find a small tab, that has some numbers stamped in to it. If you wing has the batch number 5445 stamped in to it, then you have a re-called wing.
That batch, 5445, is the only batch that has been recalled.

Q: Does my Xstreme regulator have an over pressure valve in the first stage?
A: The only Xstream regulators that has a built in over pressure valve, are those that has an article number that starts with 0100, complete regulator, or 0110, just a 1st stage.

Q: There is a problem with my Poseidon gear. What do I do?
A: The first thing you do, is to contact the dealer where you bought the item that’s casing the problem. Explain the problem to them and they will help you out if they can. If the dealer can’t fix the problem, they will in turn contact the local Distributor and if the Distributor can’t fix the problem they will contact Poseidon in Sweden. Keep in mind that you will be required to show proof of purchase and that it has to be a manufacturing- or material error to be covered by our warranty terms. Our warranty terms do not cover items sold used or problems that are related to normal wear & tare or improper handling of the equipment.


Poseidon was first to introduce the single hose regulator and have been manufacturing high-quality regulators for the last 48 years. We have learned to trust our quality and have decided to convey that confidence to our customers!

Regardless of when you purchased your Poseidon regulator, you simply enter our life-time warranty program by servicing your regulator at one of our Authorized Poseidon Service Centers. We guarantee that a Poseidon regulator purchased will be free of defects in material and workmanship under normal scuba use. The Poseidon regulator product warranty is limited to 2 years from the date of your purchase of the Product (”Warranty period”) and extended by an additional 2 years every time your Authorized Poseidon Service Centre register a service of your regulator. Warranty claims are only accepted if you register your regulator on our website and return the product to us or to an Authorized Poseidon Service Center.

How to submit warranty claims under the Poseidon Lifetime Warranty program
Warranty claims have to be submitted to an Authorized Poseidon Service Centre for inspection. If the product qualifies for warranty and proves to be defective for any reason (other then those listed in the limitations section below), Poseidon will repair or replace the Product at its own discretion at no charge. Poseidon reserves the right to replace the claimed Product with a Product of similar function and value in case the Product is no longer available.

Defects not covered by the Poseidon Lifetime Warranty Program
Only defects or damages resulting from a failure in material or workmanship are covered by the Poseidon Life-time Regulator Warranty Program.

In our opinion Poseidon Regulators are among the best....if not the best regulator for technical and public safety diving.

US Water Rescue is a fully authorized Poseidon Service Center.

You may also like

View all
Example blog post
Example blog post
Example blog post