Can't believe they sell this to people who are not trained.

[JohnnoK]

It's clearly advertised as 3000psi which means it certainly will work below 6m.

200 Bar, well capable of +6m depths, and even more dangerous as a consequence.

[AndyT]

Out of sheer interest and to test my memory I did some calcs on this .......

0.5 l tank at 200 bar gives you 100litres of free air - ie not under pressure

Assuming a Respiratory Minute Volume (RMV) of 25l per min gives you 4 minutes of breathing time - at the surface.
The 25l per minute is an average value, could be more or less given different fitness values for individuls.

Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
At 20m less than a minute and a half.

[JohnnoK]

Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
At 20m less than a minute and a half.

And, if you are stressed and anxious, it will probably be finished a lot earlier.

[C Africa]

Out of sheer interest and to test my memory I did some calcs on this .......

0.5 l tank at 200 bar gives you 100litres of free air - ie not under pressure

Assuming a Respiratory Minute Volume (RMV) of 25l per min gives you 4 minutes of breathing time - at the surface.
The 25l per minute is an average value, could be more or less given different fitness values for individuls.

Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
At 20m less than a minute and a half.

This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


C

[neoT]

Deleted, Same as post #51

[Olyfboer]

These guys say it's a scam.
https://youtu.be/pZYWO0ylFoQ

See page 3 post # 51.

[Spliffcat]

Boyles Law.

[Pietsweis]

This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


C

The no 1 and most important rule of Scuba diving.

"Never stop breathing"

That's it. No arguments. There is nothing more important, and it is with good reason

[AndyT]

This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


C

I beg to differ.

If you hold your breath until you need to breathe then you are going to take much deeper breaths to flush your lungs which ultimately will amount to the same thing as steady breathing.
Repeat that a couple of times and the air available will last even less time.

[waldo_g]

The no 1 and most important rule of Scuba diving.

"Never stop breathing"

That's it. No arguments. There is nothing more important, and it is with good reason

True.
But there is something to be said for holding your breath just a little. At 30m when viz is good, the tiny bubbles goes "ting" and the surge is minimal, perfectly adjusted buoyancy allows one to go up and down a little bit at a time by just inhaling, exhaling or holding breath at rhe right time. Direction adjustment with a twist of a fin. None of that flailing arms and scratching knees BS.

[C Africa]

Remember, my problem with these sales were that they sell them to people who are not trained scuba divers, so expect them to do stupid things.

With regard to holding your breath will use more air, not so. If you just breath normally, you are exhaling air that still has a lot of oxygen in it (or at least is not yet saturated with CO2). Personally, when I dive, I take deep breaths, and then let them trickle out VERY slowly, that way I only take one breath about every 1 minute. I know that this saves air, as my tanks always have much more air left in them than any-one else's when I surface after a dive.


C

[Gerhardvr26]

I remember these from watching Baywatch. (Alright alight, I also remember other things from Baywatch. Bouncy things).

I always really wanted one!

I thought you would have rather wanted Two of those bouncy things to play with?

[cainslie]

True.
But there is something to be said for holding your breath just a little. At 30m when viz is good, the tiny bubbles goes "ting" and the surge is minimal, perfectly adjusted buoyancy allows one to go up and down a little bit at a time by just inhaling, exhaling or holding breath at rhe right time. Direction adjustment with a twist of a fin. None of that flailing arms and scratching knees BS.

Yup. The simplest way to spot a newbie diver is by how much they move.

[Olyfboer]

Boyles Law.

Correct(P1V1)/T1 = (P2V2)/T2

Where

P - Pressure
V - Volume
T - Temperature

The laws of physics are not optional.

[Rustie]

Correct(P1V1)/T1 = (P2V2)/T2

Where

P - Pressure
V - Volume
T - Temperature

The laws of physics are not optional.

cute google

[AndyT]

Remember, my problem with these sales were that they sell them to people who are not trained scuba divers, so expect them to do stupid things.

With regard to holding your breath will use more air, not so. If you just breath normally, you are exhaling air that still has a lot of oxygen in it (or at least is not yet saturated with CO2). Personally, when I dive, I take deep breaths, and then let them trickle out VERY slowly, that way I only take one breath about every 1 minute. I know that this saves air, as my tanks always have much more air left in them than any-one else's when I surface after a dive.


C

That is called skip breathing - http://thedivingblog.com/skip-breath...0be%20avoided.

Skip breathing is basically when you interrupt your normal breathing pattern for too long by holding your breath for a few seconds, in between inhaling and exhaling. It is never recommended that you get into the habit of skip breathing since it can be very dangerous and counterproductive. By holding your breath for a few seconds, you are breaking the golden rule of scuba to always breathe. Secondly, you are actually causing CO2 to build up in your body, which will ultimately increase your breathing reflex, meaning you will breathe more and not develop an efficient-breathing technique. Finally, skip breathing and CO2 build-up will more than likely give you a post dive headache and lethargy, and in extreme cases you could even suffer a deep-water blackout, which could be fatal.

[Spliffcat]

SCUBA diving in Cape waters. Skip breathing gets entertaining when a 5 meter swell zooms over your pip. Ah the joys of being a mud prawn.
Don't go deeper than 20 m anymore and only dive tropical water now.

[Olyfboer]

cute google

Pre Google. I still memorise it from my days in the Navy and first year in the SADF's Wingfield Technical College where I was in the Boyle Division and accommodated right across the road from the Libertas Hotel in Goodwood, Cape Town. Had you read the thread completely instead of making a snide remark, you may have seen that I may know a bit about being underwater.