Why are ARO units almost extinct?

[Sbiriguda]

Why are A.R.O. units almost extinct?
Autorespiratore a ossigeno - Wikipedia
An A.R.O. in Italian is an "autorespiratore a ossigeno" that is a "(pure) Oxygen rebreather"
There are some evident disadvantages: the risk of injuries and accidents is probably higher than other types of rebreathers and air tanks + regs and they require a relatively long training. Moreover, they are limited to 6 meters of depth, possibly about 10 meters, some strong persons with a military training background can go as deep as 15 meters. On the other hand, they have some significant advantages. They are silent and can be used for several hours compared to air tanks, much cheaper than other types of rebreathers due to their simple and robust design, and pure oxygen is very easy to find since it is used for healthcare and other reasons. Especially in tropical countries it could be a good choice, since the coral reef is mostly quite close to the surface and a good part of it is already visible by using an ARO unit.
So... why not after all? They could be a cheap version of rebreather to start with

 

[tbone1004]

@Sbiriguda military background and strength has nothing to do with the bodies tolerance of high partial pressure of oxygen.

O2 rebreathers are still used extensively by militaries all over the world for stealth insurgence.

Cost of the sorb and pure o2 is prohibitive in remote locations, and complications of the units themselves compared to open circuit make them impractical.

 

[jale]

Hi
I use these O2 rbs (OMG MK1 pendular and c96) quite regularly and as Tbone said, the problems are to have a small tank of O2 at high pressure and sorb. Good when you live near your dive site.
I took a machine once to a tropical destination and as no booster was available, I have to SM a s40 with 80b of oxy. I also took with me sorb It was nice but frankly a lot of troubles for not much. I prefer to take a normal rb: same troubles but no diving restrictions
But I do like these unit and in my opinion they are a good way to learn rebreather diving.

 

[Sbiriguda]

@Sbiriguda military background and strength has nothing to do with the bodies tolerance of high partial pressure of oxygen.
O2 rebreathers are still used extensively by militaries all over the world for stealth insurgence.
Cost of the sorb and pure o2 is prohibitive in remote locations, and complications of the units themselves compared to open circuit make them impractical.

AFAIK here in Italy the legal limit for recreational use is 6 meters, some push it to 10 meters more or less which is "tolerated", while it's only in the navy that they commonly use them at about -15 meters. I don't know if they have specific gear or training, or simply push the person to their limits

I do not question your remarks on pure o2 and sorb cost, still I am curious about this. In the Maldives they have for example Maafushi island which is relatively big, it has a hospital, a jail, a psychiatric hospital, etc. etc. for sure pure oxygen must be easy to find there, don't know about the price, but I would expect it to be relatively fair. The coral reef there is ridiculously close to the towns, actually the island itself is an atoll and most of the sorrounding islands are atolls. Perhaps it's the cost of the sorb that makes it not feasible. The limitations of the oxygen rebreathers compared to open circuit instead are very clear, though I believe there is also a price difference in favor of closed circuit

 

[Sbiriguda]

I use these O2 rbs: OMG MK1 pendular and c96

May I ask where did you purchase them? The first one in particular is sold only to the military unless I am mistaken I know because I contacted the company for other products but they told me they do not sell to the civilians
SIEL Advanced Sea System

Apart from the rebs, they have plenty of nice gadgets LOL
SIEL Advanced Sea System

 

[jale]

Quite a number of people dive oxy rb and a lot of them built their unit as it is not complicated.
Limit is 6M and you can drop for a few short minutes to a few more meters but you cannot compare with soldiers who have support and are paid to take risks and are on a mission.
Finding oxy is not a pb. the pb is to have the good adaptors to transfill and a good pressure. As most of the time you won't find a 50L oxy tank at 200b, you will need a booster. If not, as i said before, you can use a s40 or s80 with a low oxy pressure but it starts to be a bit away from minimalist diving and would need an oxy clean tank and you will have to change the hose to the oxy valve of the machine.
Lime, is not really the pb if you can bring yourself a 20kg in the country as you can get a lot of hours with that in warm water

 

[jale]

May I ask where did you purchase them? The first one in particular is sold only to the military unless I am mistaken I know because I contacted the company for other products but they told me they do not sell to the civilians
SIEL Advanced Sea System

Apart from the rebs, they have plenty of nice gadgets LOL
SIEL Advanced Sea System

SIEL ex OMG products built indeed the c96 pro but you can buy the first version (c96, smaller canister) through an Italian company whose name is on the tip of my tongue but...
It is cheaper to make yours
Edit: i remember...sanosub

 

[happy-diver]

Yeah just draw a couple of lines on a piece of cardboard and make a dil capable one

or you can make a ghetto version

and then just make yourself a course

 

[jale]

Yeah just draw a couple of lines on a piece of cardboard and make a dil capable one

View attachment 631039

or you can make a ghetto version

View attachment 631040

and then just make yourself a course

Nice "Triton inspired" unit

 

[Sbiriguda]

haha LOL that's awesome but I would not trust my own gear