The diving watch category offers more than just your classic 300m steel model with a rotating bezel. Some brands have long chosen to equip diving watches with features that actually make sense underwater (and I'm not talking about a perpetual calendar here). This also applies to the watch we will be looking at today. As the name suggests, the Bühlmann Decompression 02 is the evolution of the Bühlmann Decompression 01. Designed as a professional diving instrument, it is a high-tech diving watch packed with features that go beyond a traditional diving watch. It is particularly inspired by Albert Bühlmann's original circular decompression calculator and features 17 of the most common diving profiles and a “fly-no-fly” indicator.
Professor Albert A. Bühlmann (1923–1994) was a Swiss doctor who was responsible for important research into decompression science at the University Hospital of Zurich. His influence on diving ranged from commercial and military diving to recreational diving. In particular, its ZH-L16 decompression algorithm is used to create decompression tables. Inspired by this heritage, Watch Angels launched the Bühlmann Decompression 01 in 2021, which has now been further developed into the more sophisticated Decompression 02.
A circular decompression calculator by A. Bühlmann
A decompression table is a tool that divers use to plan safe ascents and avoid decompression sickness, which occurs when nitrogen absorbed under pressure forms dangerous bubbles in the body. It indicates the maximum time a diver can spend at certain depths and, if exceeded, indicates where and how long decompression stops are required during the ascent. While modern dive computers calculate this in real time, decompression tables remain a basic safety guide, ensuring divers release nitrogen gradually and minimize the risk of injury.
A bold instrument-inspired case
Before diving (pun intended) into the watch-specific features, the first thing that catches your attention about the Bühlmann Decompression 02 is its technical looks and impressive presence. The striking design of the case with three crowns is somewhat reminiscent of the Bullhead chronographs of the 1970s. It is made of stainless steel and looks like an armor on the wrist. And at 48.5mm in diameter, it's certainly not for the faint of heart. This is not a watch for the yacht club, but to match your diving suit.
The three crowns are respectively used to wind the movement and set the time (middle crown), monitor the double decompression dial (right crown), and lock/unlock the double decompression bezel (left crown). The case back is secured with 8 screws and is concave for increased comfort. The case is tilted at 5 degrees to make it easier to read.
The Bühlmann Decompression 02 has a solid water resistance of 575 m, a nod to Bühlmann's record that he set in the Zurich hyperbaric chamber. With this rating, it is well prepared to follow you well beyond the golden zone of 10 to 30 meters, the most comfortable and safe depth range for recreational divers.
Designed as a professional diving instrument, the Bühlmann Decompression 02 has a helium pressure relief valve integrated into the left crown. Below a depth of 70 meters, the air becomes toxic due to the increased pressure. Divers who dive this deep using diving bells or submersibles breathe air saturated with helium to avoid the risk of inert gas anesthesia. Helium is one of the smallest elements; This means it penetrates into the watch where no water can penetrate. During prolonged stays in a pressurized environment, the pressure inside the watch (initially surface pressure) gradually increases to the pressure of the diving depth. The depressurization causes a problem when the diver ascends, or more precisely, returns to surface pressure. Without a helium release valve to allow pressure to escape beyond a certain level, the pressure can cause the crystal to pop out.
As you would expect from a proper diving watch, the Bühlmann Decompression 02 features an easy-to-read minute hand that provides the most important information that needs to be monitored while diving. The hour hand, on the other hand, has a minimalist design. The second hand features a red, luminous, arrow-shaped tip. As with all diving watches, its function is crucial as it allows you to check whether the watch is still running. If the watch were to stop, even for a short period of time, it could give an incorrect reading of elapsed time, which can be dangerous when attempting decompression.
Double decompression bezel and double decompression dial
Now that we've gotten the basics down, it's time to take a look at the specific features of this unique diving watch. The Bühlmann Decompression 02 is the first diving watch with what the brand calls the Bühlmann Twin Safety Bezel, a diving bezel that allows separate tracking of total diving time (TDT) and decompression stops (DS), each with its own blocking direction. The latter can only be operated when the 11 o'clock crown is released.
The decompression stop times for 17 dive profiles are indicated on the Bühlmann Twin Dive Dial and come from Dr. A. Bühlmann. The diving profile can be selected by turning the lower dial via the right crown. The profile data and the associated decompression stop time can be viewed and selected in the section at 6 o'clock.
In fact, the bezel is zeroed for the entire dive time (inner bezel) by aligning the 0 mark with the minute hand at the start of the dive. Once the bottom depth is reached, the selected dive profile allows the dive to be monitored. When it is time to surface, the ascent is monitored with decompression stops at 9m, 6m and 3m using the external decompression time scale.
Decompression 02 focuses on the “Golden Zone” dive profiles with the 17 most common dive profiles for single tank dives up to 39 meters, for dives at altitudes from 0 to 700 m above sea level, as indicated on the dial.
A rare feature: At the end of the dive, the lower dial is set to the “Fly-No-Fly” position and the corresponding display is set to “No-Fly” using the “Date” setting position of the center crown. An arrow points towards the red zone. Once an arrow points to the green zone, it is safe to fly once a minimum 24-hour ban has expired (the “Min” display means “Check” as the date wheel may not jump for 12 hours).
Movement, availability and price
Inside the Bühlmann Decompression 02 is the proven caliber SW-300. This clone of Sellita's ETA 2892 is 25.60 mm in diameter, beats at 4 Hz and has a power reserve of at least 50 hours. The stop-second mechanism allows for precise adjustment.
The Bühlmann Decompression 02 comes on a perforated rubber strap, which, thanks to its design, allows for a wide range of adjustment options. The buckle side of the strap is articulated, while the back is integrated into the lugs. The brand's logo is engraved on the large, solid pin buckle. The watch is released in a limited edition of 575 pieces and the price is set at CHF 3,990. It can be purchased exclusively on watchangels.ch.
A portion of each sale is donated to the DAN Europe Medical Research Foundation to support their ongoing research into the perfect decompression algorithm.
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