ISO 6425

Every watch in the HELM collection that bears the "DIVER'S" designation on the dial or caseback meets the requirements of ISO 6425:2018 and has been individually tested in water at a pressure equivalent to 125% of the watch's rated depth.

WHAT IS ISO 6425?

The ISO 6425 standard, first published in 1982, identifies the minimum requirements any watch designed to withstand diving in water at depths of at least 100 meters must satisfy. The most current edition of the standard was published in 2018.

The standard was created to help distinguish watches that are suitable for diving from "dive style" watches and other water resistant watches that may not be suitable for diving. Only watches that satisfy the requirements of the test standard will bear the designation "DIVER’S L m" or "DIVER'S WATCH L m" (where "L" indicates the rated diving depth in meters).

WHAT DOES IT MEAN?

Purchasing a watch that is ISO 6425 compliant means you can be confident your watch will perform as intended. It means your watch includes specific features and meets specific criteria that any watch being used for diving should. In practical terms, it means that before your 300m watch takes its first dip in the water on your wrist, it's already been to 375 meters and back, without issue.

WHO IS ISO?

ISO (International Organization for Standardization) is a worldwide federation of member bodies from different nations who work together to create international standards. Creating ISO standards is normally carried out through ISO technical committees. Any ISO member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. In addition, both government and non-government international organizations, in liaison with ISO, may take part in the process.

Once the technical committee creates a draft of a new standard, it is circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75% of the member bodies casting a vote.

You can read more about ISO on their website.

WHAT DOES THE TESTING INVOLVE?

To meet the requirements of ISO 6425 and bear the "DIVER'S" designation, watches must include several specific features and pass several specific tests. Some of the tests are applied to every single watch (100% testing) while others are applied to a portion of the watches produced (type or batch testing).

BASIC FEATURES & CRITERIA

Any watch that bears the "DIVER'S" designation must include the following features and meet the following criteria:

1. It must include a diving time indicator, such as a unidirectional rotating bezel or a digital display,
    which is protected against inadvertent rotation or accidental manipulation. If the diving time
    indicator is a rotating bezel, it should include a minute scale going up to 60 minutes, with clear
    markings indicating every 5 minutes. If there are markings on the dial, they should be coordinated
    with the markings on the bezel and clearly visible. If the diving time indicator is a digital display, it
    should be clearly visible.

2. It must include an indication that the watch is running and this indication must be visible in total
   darkness (usually accomplished with a second hand that has a luminous tip or tail).

3. The following elements of the watch must be legible at a distance of 25 cm (9.8 in) in the dark for
     at least 180 minutes after exposure to light:
     - The time (with a minute hand that is clearly distinguishable from the hour hand).
     - The set time of the diving time indicator.
     - An indication that the watch is running (such as a second hand with a luminous tip or tail).
     - In the case of battery powered watches, a low battery life indicator.

100% TESTING

Every complete watch must pass the following water resistance test.

1. Water Overpressure Test: The watch is submerged in water in a pressure chamber. An overpressure
     of 125% of the rated pressure is then applied within one minute and maintained for two hours.
     Subsequently, the overpressure is reduced to 0.3 bar within one minute and maintained at this
     pressure for one hour. The watch is then removed from the water and dried. The condensation test
     is performed before and after this test.

2. Condensation Test: The watch is placed on a heated plate at a temperature between 40°C and 45°C
    until the watch has reached the temperature of the heated plate. A drop of water, at a temperature
    of 18°C to 25°C is then placed on the glass of the watch. After one minute, the glass is wiped dry and
    the inside surface of the glass is inspected for any signs of condensation, which would indicate
    moisture (water intrusion) inside the watch. This test is conducted before and after the overpressure
    test.

The above pressure test is conducted in static (still) water. This means that a watch with a 300 meter depth rating (30 atm) will be water resistant if it is stationary under 375 meters of static water (37.5 atm of pressure).

The water resistance testing required by ISO 6425 for dive watches is fundamentally different from the less stringent water resistance testing required by ISO 2281 for non-dive watches. The latter does not require testing every watch, and those watches that are tested are subjected only to a pressure equal to their rated depth and for only 10 minutes.

TYPE TESTING:

A portion of watches from every production batch must pass these additional tests:

1. Resistance to a Magnetic Field: The watch is exposed in three positions (for mechanical watches)
    or in the most critical direction (for quartz watches) to a direct current magnetic field of 4800 A/m.
    The watch must not stop during the test and mechanical watches must maintain their accuracy
    to ± 30 seconds/day as measured before the test.

2. Resistance to Shock: The watch is subjected to two shocks (one on the 9 o'clock side of the case,
    and one perpendicular to the face of the watch) which simulate a fall from 1 meter onto a
    wooden floor. The shock is usually delivered by a pendulum impact hammer which delivers a
    measured amount of energy (specifically, a 3 kg hammer with an impact velocity of
    4.43 meters per second). The watch must maintain its accuracy to ± 60 seconds/day (mechanical)
    or ±2 seconds/day (quartz) as measured before the test.

3. Resistance to Salt Water: The watch and bracelet are submerged in a 30 g/l sodium chloride solution
    (salinity comparable to normal seawater) and kept there for 100 hours at 18 °C to 25 °C. After this
    test, the case and accessories are examined for changes. Moving parts, particularly the rotating bezel,
    are checked for proper functioning.

4. Resistance to Thermal Shock: The watch is placed at a temperature of -20°C in air for 60 minutes.
    After standing at room temperature for 30 minutes, it is then placed at a temperature of 60°C in air
    for 60 minutes. Then within 5 minutes, the watch is submerged in water at a temperature of 2°C for
    60 minutes. The condensation test is performed before and after this test.

5. Reliability Under Water: The watch is submerged in water to a depth of 30 cm for 48 hours at 18°C
    to 25°C. During immersion, all mechanisms must continue to function properly. The condensation
    test is performed before and after this test.

6. Resistance to External Force (Attachments): The strap or bracelet of the watch being tested is
    closed and a force of 200 N (45 pounds-force) is applied to each spring bar (or attachment point)
    in opposite directions. The watch is then inspected to ensure no damage has occurred to the
    watch or attachment points.

7. Condensation Test: The watch is placed on a heated plate at a temperature between 40°C and
    45°C until the watch has reached the temperature of the heated plate. A drop of water, at a
    temperature of 18°C to 25°C is then placed on the glass of the watch. After one minute, the glass
    is wiped dry and the inside surface of the glass is inspected for any signs of condensation, which
    would indicate moisture (water intrusion) inside the watch. This test is conducted before and after
    the testing for thermal shock resistance, reliability under water and resistance of crowns and
    setting devices to external force.

MIXED-GAS / SATURATION TESTING

ISO 6425 requires additional testing for watches intended for mixed-gas or saturation diving (which involves long term exposure to Helium/Oxygen gas mixtures). Currently, HELM watches are only tested as "air divers". They are not tested to meet mixed-gas diving requirements and are therefore not intended for use during mixed-gas or saturation diving.