Drysuit Inflation Bottle: When You Need One and Why

Cold water. A long decompression. Back gas with helium in it.

Every time you add gas to your suit, you're adding something that pulls heat out of you. Helium carries heat away far faster than air. So the colder and longer the dive, the more every squirt of back gas into your suit costs you.

That's the problem a small bottle on your rig solves.

What is a drysuit inflation bottle?

A small, separate cylinder that feeds your drysuit and nothing else. It has its own regulator and one hose to your suit valve. Most divers fill it with argon.

It doesn't replace your back gas. It replaces your back gas as the thing you put in your suit.

Do you need one?

Probably not yet.

For most recreational drysuit dives, your back gas inflates your suit just fine. A separate bottle starts to make sense when:

• Your back gas contains helium. That's the big one. Helium in your suit is helium pulling heat out of you.
• The dive is long and cold, with a lot of time spent still at your stops.
• You want suit gas separate from breathing gas, so a suit problem never touches the gas you breathe.

Does argon actually keep you warmer?

Let's be honest about this one.

The comfortable belief: argon is the secret to staying warm.

The truth: argon conducts heat a little less than air, so it insulates a little better. How much difference you'll actually feel is debated. Your undergarment, your hood, your gloves and how much you move matter far more.

The real reason on a trimix dive is simpler: you're not putting helium in your suit.

What can go wrong?

• Somebody breathes it. Argon is not breathable. Mark the bottle clearly, so nobody grabs it as a pony bottle. Ever.
• It runs out. A small bottle doesn't last forever. Know how full it is before you dive.
• The valve is closed when you need it.
• You can't reach it. If you can't reach the valve, you can't deal with a stuck inflator.

Where the bottle mounts, which regulator it uses and how you manage it underwater are set up with you, on your rig, as you move into helium diving.

Is it time for one?

Ask yourself honestly. Are you breathing helium yet? Are your dives getting longer and colder? Is your suit the thing you're thinking about at the end of every dive?

If the answer is no, spend the money on a better undergarment and better drysuit buoyancy control. Either way, it starts with real drysuit skills. That's the Drysuit Diver course.