History of the Poseidon Cyklon Regulator (1958–1993)

The Poseidon Cyklon regulator has a storied history dating back to the late 1950s. Ingvar Elfström – a young Swedish diver and engineer – founded Poseidon in 1958 (originally under the name Aqua-Sport) with the goal of solving diving equipment problems. Lacking suitable gear on the market, Elfström began building his own regulators. He first produced a twin-hose model called the “Poseidon Senior” (manufactured in his kitchen in 1955–1957), but quickly turned to a new single-hose design. In 1958, Elfström (with collaborator Rolf Tisrand and co-founder Dennis Österlund) introduced the Poseidon Cyklon Junior, which was the world’s first single-hose scuba regulator produced in series. Unlike the traditional double-hose “Aqua-Lung” units of the era, the Cyklon’s demand valve was located at the mouthpiece on a single hose – a groundbreaking design that set a new world standard for regulators. This innovation provided easier breathing and a more compact, reliable setup, and it quickly gained popularity, especially among professional and cold-water divers.

Throughout the 1960s and 1970s, the Cyklon underwent continuous refinement while staying true to its original concept. The early model (Cyklon Junior) was soon updated – in 1962 an improved Cyklon Sport version was launched to further enhance performance. By the late 1960s, Poseidon had dropped the “Junior/Sport” labels and the regulator became simply known as the Poseidon Cyklon. Internally, it was an unbalanced diaphragm first stage design (marketed as “compensated” at the time) paired with a unique downstream second stage. This mechanism was gradually improved over the years based on divers’ feedback and technology advances. Notably, Poseidon added more ports to the first stage (early Cyklons had only a single low-pressure hose port for the second stage) to accommodate inflation hoses and alternate air sources as the sport evolved. The Cyklon’s second stage retained its distinctive side-exhaust, circular diaphragm design, which allowed it to be used in any orientation or from either the left or right side – a rare ambidextrous feature even decades ago. This made the Cyklon very flexible for divers and was one reason it gained a reputation as a rugged “workhorse” regulator.

Several milestones marked the Cyklon’s evolution leading up to 1993. In the early 1970s, the regulator’s first stage was upgraded and eventually became known by the model name Cyklon 300. (The “300” moniker alluded to its 300-bar pressure rating and improved internals, effectively the same core design as the original Cyklon Junior but with enhancements.) By the late 1970s and 1980s, Poseidon introduced optional polymer components for the second stage – models like the Cyklon Super featured a lighter plastic second-stage housing – while the classic brass/metal construction remained available for maximum durability. Throughout these changes, the fundamental operation of the Cyklon stayed consistent: a robust downstream valve second stage and a cold-resistant diaphragm first stage. In fact, cold-water performance was a hallmark of the Cyklon from the start. Poseidon regulators were born in the icy waters of Sweden, and the company pioneered solutions to prevent regulator freeze-up. For example, earlier Cyklon first stages could be fitted with an environmental sealing cap filled with antifreeze fluid (even vodka or glycerin mixtures) to keep the mechanism from icing in extreme conditions. This reliability in harsh environments made the Cyklon popular with military and expedition divers; Cousteau’s research teams reportedly used Poseidon Cyklons during Antarctic expeditions for their superior cold-water functionality. By the 1980s, many naval and rescue units had adopted the Cyklon – it became the regulator of choice for the German Navy, the Royal Swedish Navy, and even the US Submarine Rescue Team, thanks to its renowned toughness and performance.

By the early 1990s, the Cyklon’s basic design had been proven for over three decades, but Poseidon prepared a significant update. Up to that point, all Cyklon variants used an unbalanced first stage, meaning breathing resistance would increase as tank pressure dropped. In 1993, to commemorate the longevity of the model and introduce a modern improvement, Poseidon developed the Cyklon 5000 – which for the first time featured a balanced diaphragm first stage for steadier performance at all pressures. Apart from the internal balancing, the Cyklon 5000 was essentially the same classic regulator (the second stage design and overall appearance remained largely unchanged). The introduction of the balanced Cyklon 5000 in 1993 marked a major milestone in the regulator’s evolution, effectively retiring the original Cyklon 300 unbalanced version after 35 years of service. To send off the venerable design in style, Poseidon released a special commemorative model that year – the famed Gold Anniversary Edition Cyklon.

The 1993 Gold Anniversary Edition – Features and Specifications

Poseidon’s limited-edition Cyklon “Gold” regulator (1993) shown in its teak presentation case. Only 500 of these gold-plated Cyklon 300 regulators were produced, each accompanied by a signed certificate from founder Ingvar Elfström.

In 1993 Poseidon Diving Systems unveiled a Gold Anniversary Edition of the Cyklon regulator to celebrate the model’s decades of success. This was a limited series of 500 units, each built upon the Cyklon 300 design and lavishly finished for collectors and loyal users. The regulator’s second stage and first stage were plated in 24-karat gold, giving it a striking appearance. Each unit was individually numbered (e.g. “196/500”) and engraved with commemorative markings on the first stage, including the text “CYKLON 300” and the year 1993). Rather than a standard cardboard box, the Gold Cyklon came packaged in a hand-crafted teak wood presentation case, complete with an etched Poseidon logo. Inside, Poseidon included a scroll detailing the history of the Cyklon design and an exclusive Poseidon lapel pin – items available only with this anniversary set. A certificate of authenticity was also provided, personally signed by Ingvar Elfström, the inventor of the Cyklon, shortly before his passing. All of these touches underscored the significance of the occasion and the company’s pride in its flagship regulator.

Technically, the Gold Anniversary model was identical to the late-version Cyklon 300 (unbalanced diaphragm first stage and downstream second stage), except for its gold-plated exterior. It was fully functional for diving; however, Poseidon intended it primarily as a collectible tribute piece. The gold plating, while durable, would not withstand heavy use without wear, so most owners kept these regulators as display items. The commemorative edition was timed to coincide with the launch of the new balanced Cyklon 5000, highlighting the transition to the updated design. In essence, the Gold Cyklon represents the culmination of 35 years of continuous development – it was the “last hurrah” of the classic model that began in 1958, making way for the next generation. Poseidon produced only 500 of these Gold regulators, making them extremely rare and sought-after among vintage diving equipment enthusiasts (often appearing only occasionally in collector markets). The Gold Anniversary Cyklon thus holds a special place in diving history, symbolizing both the legacy of one of the world’s longest-lived regulator designs and the dawn of its modern successor.

Poseidon Diving Systems: Company Background and Innovations

Poseidon Diving Systems (based in Gothenburg, Sweden) has been a pioneering force in the diving equipment industry since its founding in 1958. The company was founded by Ingvar Elfström together with Dennis Österlund, initially under the name “Aqua-Sport”. From the very start, Poseidon distinguished itself by introducing the first single-hose regulator to the world – an invention that forever changed scuba diving by replacing the bulky double-hose systems of the early 20th century. This achievement securely placed Elfström among diving’s great engineering pioneers, and it set the tone for Poseidon’s culture of innovation. As the company grew (opening its first dive shop in 1958 and expanding production from Elfström’s kitchen to a garage workshop), the brand name was changed to Poseidon for broader appeal. The original Cyklon regulator became a commercial success, especially among professional and military divers, establishing Poseidon’s reputation for rugged, reliable gear.

Over the ensuing decades, Poseidon Diving Systems introduced key innovations that pushed diving technology forward. In the late 1970s, Poseidon developed the Jetstream regulator (released in 1978), which featured a revolutionary servo-assisted second stage. The Jetstream’s valve design delivered extremely high airflow with low breathing effort, even at great depths, and it included an upstream servo valve with an over-pressure relief – a unique approach at the time. (The Jetstream, also known as the “Poseidon Odin” in some markets, became a favorite among deep divers and tech diving communities for its performance.) In the early 2000s, Poseidon followed up with the Xstream regulator (launched in 2002), further improving reliability and depth performance. The Xstream was certified for mixed-gas (technical) diving to depths beyond 150–200 meters and introduced an advanced “Thermo Dynamic Anti-freeze” system to prevent ice formation without external fluids. These regulator innovations – from the first single-hose Cyklon to the Jetstream and Xstream – cemented Poseidon’s role as an industry leader in breathing apparatus design.

Beyond open-circuit regulators, Poseidon also expanded into other cutting-edge diving equipment. The company developed some of the first truly user-friendly rebreathers for recreational divers. Notably, Poseidon’s Discovery MkVI (released in 2006) and its successor the SE7EN (2012) were electronic closed-circuit rebreathers designed to bring military/technical-grade rebreather technology to sport divers. Poseidon’s advancements have earned it a respected place in the diving world – the company has even been a selected equipment supplier to the Swedish Royal Family, warranting a royal seal of approval for its quality. Today, Poseidon continues to serve demanding users such as navy dive teams, rescue units, and technical explorers worldwide. With a philosophy of “improving but never copying,” Poseidon has consistently prioritized quality, safety, and innovation in its gear. From the 1958 Cyklon regulator that pioneered the single-hose design, to modern developments in high-performance regulators and rebreathers, Poseidon Diving Systems has played a pivotal role in shaping the equipment that keeps divers breathing safely underwater

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