Let’s talk about when and where to use a Helium escape valve, both the automatic and manual types. I have a few diver’s watches with Helium escape valves, and the rest of my dive watches don’t have them.
I’ve been diving since my military days, but back then, I hated it because I couldn’t see anything underwater. Nowadays, I enjoy recreational diving(sometimes Technical diving), which is much more pleasant since I only go to beautiful places.
When diving in tropical regions, conditions can be rough, and it’s often unsafe to leave valuables in your room or on the boat. That’s why I always take my dive watch with me, though, of course, if you feel uneasy, it’s better to leave valuables behind. Always be mindful of your belongings.
The gas used for diving varies depending on the situation. Most recreational divers use tanks filled with approximately 21% oxygen and 79% nitrogen (regular air that’s been dehydrated, filtered, and compressed). If you have an Enriched Air (Nitrox) Specialist certification, you can safely adjust the oxygen-nitrogen ratio and dive up to 40 meters based on the circumstances.
When diving deeper than 40 meters, it’s considered Technical diving, and for dives below 65 meters, Tri-mix (a gas mix) is used to prevent decompression sickness. Tri-mix consists of oxygen, nitrogen, and helium, and it’s primarily used to reduce the narcotic effect of nitrogen (nitrogen narcosis) and prevent oxygen toxicity in deep dives. Dives up to 40 meters are typically non-decompression dives, while decompression dives start from 40 meters and beyond. Saturated diving, or SAT diving, is a type of decompression dive and falls under Technical diving.
As many of you know, the Helium escape valve was invented specifically for saturated diving, where helium is used.
Helium escape valves were designed for Tri-mix SAT dives. These are long-duration dives where decompression is a critical concern. During such dives, the tiny helium molecules can penetrate the watch case and remain trapped inside. (Depending on the dive plan, a dive of around 100 meters can require at least 1 hour and 30 minutes of decompression time.)
During decompression, the helium inside the watch can expand and cause the glass to pop off. That’s where the Helium escape valve comes in—to release the helium that infiltrated the watch during decompression. (Thanks to advancements in technology, many modern dive watches can withstand this pressure or have cases and glass that prevent helium penetration, so they don’t need a Helium escape valve.)
For salvage operations in open waters or tasks in good conditions, SAT dives often involve the use of diving bells or chambers, where the Helium escape valve is used. For projects like constructing bridges, air pockets are created at the base of columns for long-term work. (In the illustration below, the Red area represents an air pocket, and Tri-mix is supplied as shown by the Green line.)
In these cases, divers climb ladders built into the bridge columns to decompress on their way up, using the Helium escape valve while still underwater. If your job isn’t related to this field, though, you’ll probably never need to use a Helium escape valve.
Appendix
From this explanation, I can further expand on the waterproofing details in the “Series: Urban Myths About Watches – Waterproofing, Part 2“
When humans breathe, the amount of water vapor in inhaled and exhaled air is as follows:
- Inhaled air:
- Water vapor (H₂O): around 0.1% to 1% (depending on the environment)
- The humidity of inhaled air varies with the atmospheric humidity, so it’s low in dry environments and higher in humid ones.
- Exhaled air:
- Water vapor (H₂O): around 5% to 6%
- Since exhaled air is moistened within the body, it always contains nearly saturated water vapor.
But during a dive, unlike regular air, the breathing gas mixture (usually composed of nitrogen, oxygen, and helium) is controlled. The helium concentration in Tri-mix depends on the depth of the dive, and typical helium percentages are as follows:
1. Shallow Saturation Diving (60–100m):
- Inhaled gas:
- Helium (He): around 20% to 30%
- Oxygen (O₂): around 21%
- Nitrogen (N₂): the rest (49% to 59%)
- Water vapor (H₂O): almost none (usually close to 0% due to dried, filtered, compressed air; hence, you get quite thirsty after long dives).
- Exhaled gas:
- Helium (He): around 20% to 30% (an inert gas, so it’s all exhaled)
- Oxygen (O₂): around 16% (after usage during breathing)
- Nitrogen (N₂): around 49% to 59%
- Carbon dioxide (CO₂): around 4%
- Water vapor (H₂O): around 5% to 6% (moisturized air from the body)
2. Deep Saturation Diving (100m+):
- Inhaled gas:
- Helium (He): around 30% to 70%
- Oxygen (O₂): around 10% to 18%
- Nitrogen (N₂): the rest (12% to 60%)
- Water vapor (H₂O): almost none.
- Exhaled gas:
- Helium (He): around 30% to 70%
- Oxygen (O₂): around 5% to 16%
- Nitrogen (N₂): around 12% to 60%
- Carbon dioxide (CO₂): around 4%
- Water vapor (H₂O): around 5% to 6%
As seen here, exhaled air contains far more water vapor than inhaled air, as moisture from our bodies evaporates and is expelled with each breath. Yet, in high-pressure environments such as decompression chambers or working spaces during Tri-mix diving, while the watch is exposed to constant humidity, the watch’s robust waterproof system prevents water molecules (which are larger than helium molecules) from penetrating, even as the helium seeps in.
