Why would you need to switch gases?

[mishellanious]

Hi all,

I'm looking at buying a dive computer but I don't understand why the average person would need to switch gases during a dive. So for example, I'm looking at the Suunto D6i which can do air and nitrox and can switch between two gases. Is the only reason for this if you were to put two tanks on your back? Or is it just for ease between repetetive dives so that you can set everything in the morning and be good for your two dive boat trip? I don't understand why non-technical divers would need this feature.

Any input appreciated, Thanks!

 

[dreamdive]

No, you don't need it. However on my Shearwater I can select the gas I am diving. For recreational divers, you can have a nitrox and an air setting for example. You are correct that you would not perform a gas switch during your dive. I don't know the Suunto, but on the Shearwater you have to turn the gas on/off you are diving or else the computer does not know what you are actually using.

 

[ontdiver]

The short answer is that for recreational diving, you will never have to switch gases (not to be confused with Nitrox settings). While I'm not familiar with the D61, a number of dive computers have features that allow divers to make the transition from rec to tec .....and gas switching. Bottom line though, get a good computer that is versatile, user friendly and has good reviews. If you buy an inexpensive "entry level" dive computer you may regret the decision a couple of months later.

 

[tbone1004]

actually that's not entirely true.

Many divers will carry a pony bottle that may have a different mix in it. I.e. air instead of nitrox to avoid any MOD issues at depth, or nitrox instead of air to aid in decompression efficiency. It's more accurate to have that put in there, and more importantly IF you decide to go into any light technical diving, it allows you to do O2 decompression which is one of the best courses any diver can take. It not only makes the whole diving experience safer by expediting mandatory decompression stops, but can also ease a divers mental state when he is pushing NDL's, or provide an added safety buffer by performing your precautionary stop on O2 instead of backgas.

 

[Lorenzoid]

I don't understand why non-technical divers would need this feature.

My answer is that your intuition is correct: Non-technical divers do not "need" gas switching, and most will never use it. My suspicion as to why seemingly every computer available today now has gas switching is that it is largely marketing hype. If I am not mistaken, surveys of newer divers have indicated that a great many express an interest in progressing into technical diving. My suspicion is that manufacturers take advantage of new divers' interest (and the growing interest in general) in tech diving by advertising their computers as being capable of handling the divers' future needs. In reality, most of the rec divers who thought gas switching would be a pretty cool feature to have should the need arise in the future, and were swayed by that in their decision of what computer to buy, never end up using it. Most rec divers remain rec divers. And even the minority who eventually get into tech diving often end up getting a different computer by the time they reach that point in their diving, often years down the road.

As for the underlying question of what computer to get, there are dozens and dozens of threads on SB where people have asked that question, so if you take the time to sift through them you will get a sense of what features more experienced people think are important and what are less important.

 

[ontdiver]

actually that's not entirely true.

Many divers will carry a pony bottle that may have a different mix in it. I.e. air instead of nitrox to avoid any MOD issues at depth, or nitrox instead of air to aid in decompression efficiency. It's more accurate to have that put in there, and more importantly IF you decide to go into any light technical diving, it allows you to do O2 decompression which is one of the best courses any diver can take. It not only makes the whole diving experience safer by expediting mandatory decompression stops, but can also ease a divers mental state when he is pushing NDL's, or provide an added safety buffer by performing your precautionary stop on O2 instead of backgas.

Absolutely, but for the average recreational diver, the pony/deco narrative is definitely light tech. All good, though, and an important consideration when considering new gear.

 

[Dhboner]

It's functionality that is there if you need it down the road. Would you still buy a 1080P television even if you didn't own any blue-rays? It doesn't hurt to have it (if you can afford it) and then your are set if you ever buy a blue-ray. So if you can afford a computer that allows you to switch gasses during a dive then you may as well get it...who knows how you will progress as a diver.

 

[skankpile]

gas switching computer don't beep and annoy you so much. Cochran is an exception to that rule

 

[tbone1004]

skankpile, that's not true at all. Certain gas switching computers don't, hell the Shearwaters don't actually have the ability to beep or vibrate or anything like that.

For me, there are a few criteria that are very important when purchasing a computer
MUST have gauge mode, this is not optional. If it doesn't, you have a useless paperweight if you ever go into technical diving

MUST have at least 2 gasses. It doesn't actually cost the manufacturers any more to make these, they already have algorithms made with multi gas and it is all of like 10 lines of programming to program the gas switch. Same reason as above, 2 gas computers with gauge mode are the sweet spot, allows you to "ride the computer" for light technical diving, i.e. extended bottom time at 100ish feet with relatively short O2 decompression, and has gauge mode if you get into more gasses or want to dive tables

Preferably have user replaceable battery. None of this have to take it to a dive shop to change the battery bs.

Preferably has avg. depth function. My primary dive buddy disagrees on the importance of this, but I track my SAC rate for every dive as it is a very good indicator of how I was feeling on said dive. Without avg depth it is pretty much impossible.

Preferably have easy log uploads to computer without stupid $100+ proprietary cable. This is the least important, but if shopping for a long term computer it is nice if it has BT upload capability or some other easy and cheap upload capability.

 

[Lorenzoid]

It's functionality that is there if you need it down the road. Would you still buy a 1080P television even if you didn't own any blue-rays? It doesn't hurt to have it (if you can afford it) and then your are set if you ever buy a blue-ray. So if you can afford a computer that allows you to switch gasses during a dive then you may as well get it...who knows how you will progress as a diver.

Interesting analogy. It would be interesting to see statistics on how many people who buy a new TV buy a Blu-ray disc player before buying their next TV versus how many newly certified divers who buy a new computer get into tech diving before buying their next computer.