Semi Closed Rebreathers Vs. Open Circut Rebreathers

[PaulSmithTek]

I was wondering what the difference is. I see some post about re breathers and people talking about them. I know the basic theory behind re breathers. I would just like to know the difference.

Thanks,

[JeffG]

Semi Closed vs Closed


There is no such thing as an Open Circuit Rebreather.

[Mr.X]

Semi Closed vs Closed


There is no such thing as an Open Circuit Rebreather.

Yes there is. Simply forget to connect a hose to the loop.

I would suggest a quick google search or visit Rebreatherworld.com and see tons of pictures there.

[JeffG]

Yes there is. Simply forget to connect a hose to the loop.

blub blub blub blub

[Kevrumbo]

I was wondering what the difference is. I see some post about re breathers and people talking about them. I know the basic theory behind re breathers. I would just like to know the difference.

Thanks,

Here are two good basic overviews:
http://www.tmishop.com/RB%20newbies.htm
http://www.rebreatherworld.com/3114-post3.html

[caveseeker7]

was asked a little while back, and the answer included the differences between different types of rebreathers.

[Spoon]

basically the difference is that the scr expells "some" of the gases in the form of bubbles as part of its normal operation why the ccr reuses all gasses as it passes the breathing loop.

[BigJetDriver]

basically the difference is that the scr expells "some" of the gases in the form of bubbles as part of its normal operation while the ccr reuses all gasses as they pass around the breathing loop.

Spoon,

You are correct in what you say, but this is more of a description of effect rather than function.

The semi-closed units could best be described as "gas extenders". They feed a small amount of fresh gas from your cylinder either continuously, or when a mechanical control device senses loop volume depletion. They feed a little more than is needed, to provide a safety margin, and vent the excess overboard when necessary.

The fully closed units sense the oxygen percentage (in terms of partial pressure) in the gas you are breathing. They then inject just enough oxygen to make up for the amount your body uses. If you remain at one level in the water column, no gas will be vented because you get exactly what is required, and no more.

It must be noted that all rebreathers will vent gas on ascent due to volumetric expansion.

This is the quick and dirty explanation, but those are the basic differences. Hope that helps!

[debersole]

I agree totally with what has been said above. The other practical difference between SCR and CCR is that the SCR gives you a fixed FIO2 and your PO2 will vary by depth. A CCR keeps your PO2 fixed while "FIO2" will vary by depth. This means that an SCR will have depth restrictions similar to diving nitrox because of PO2 limitations which you do not have with CCR.

[Spoon]

Spoon,

You are correct in what you say, but this is more of a description of effect rather than function.

The semi-closed units could best be described as "gas extenders". They feed a small amount of fresh gas from your cylinder either continuously, or when a mechanical control device senses loop volume depletion. They feed a little more than is needed, to provide a safety margin, and vent the excess overboard when necessary.

The fully closed units sense the oxygen percentage (in terms of partial pressure) in the gas you are breathing. They then inject just enough oxygen to make up for the amount your body uses. If you remain at one level in the water column, no gas will be vented because you get exactly what is required, and no more.

It must be noted that all rebreathers will vent gas on ascent due to volumetric expansion.

This is the quick and dirty explanation, but those are the basic differences. Hope that helps!

thanks rob, im still learning everyday. still havent decided whether i wanna go scr or ccr. will do more research.