Saffadiver
Contributor
Imagine an alternative universe where we use helium in our BCDS (we still have a tube for breathing air). What would happen? So I asked Nevill (my chatGpt)
In technical diving:
What Happens If You Fill a BCD or Drysuit with Helium?
1.
- Helium is a gas, so filling a BCD with it will still displace water and create buoyancy.
- However, helium is much less dense than air — about 1/7th the weight of air at surface pressure.
- So, the mass of the gas you're carrying is lighter, which affects weighting and buoyancy control over the dive.
2.
- Helium compresses and expands more predictably and rapidly than air due to its physical properties.
- That means buoyancy changes more quickly with depth, potentially making fine control harder without practice.
3.
- In drysuits: helium conducts heat much faster than nitrogen — it's terrible for insulation.
- Divers avoid using helium for suit inflation. It's common to use a dedicated small cylinder of argon (which is excellent for thermal insulation) for drysuit inflation on deep dives with helium breathing mixes.
4.
- Helium is expensive and hard to source.
- It doesn’t offer better lift in any meaningful way — just lighter gas weight, which can throw off your weight calculations.
Real-World Diving Use
In technical diving:
- Breathing gas may include helium, but BCDs and suits are still inflated with air (or argon for suits).
- Using helium for buoyancy inflation is avoided due to cost, thermal issues, and unnecessary complexity.
TL;DR
- Yes, helium can be used for buoyancy — it works physically.
- But it's not practical or advisable:
- It’s poor for thermal insulation (especially in suits).
- More sensitive to pressure changes.
- Adds complexity without real-world benefits.
- Expensive and wasteful.
