Rebreather question

[Chuck_Northrup]

Andre had a rebreather malfunction that meant he was getting pure oxygen before it could be remedied.

The Inspiration always adds pure oxygen, except when diluent is used (typically only upon descent) so the addition of pure o2 is not a “malfunction”.

This was a situation that was unnerving at 50m but would have been much worse at 100m which is where he was going to be for me.

There are several “situations” which could lead to rapid o2 addition. The two most likely would be a stuck manual inflator and/or a stuck solenoid. More on this later.

Their emergency procedures were excellent and everybody was completely safe

I agree completely. Obviously these were well trained divers and were diving within their limitations.

but it did make us wonder if we were being controlled by fate today.

Tanya is constantly pushing the envelope and trusts quite a bit more to “fate” than a rebreather diver doing similar depths. The rebreather diver knows s/he has enough gas, Tanya may not.

I assume his handset was working correctly so that he see he was getting to much 02 and he then went to manual mode.

All he would have to do is shut of o2 and possibly (but not necessarily) a dil flush. He would only need to go manual if the solenoid was failed open. He may have had a high po2 alarm and noticed the high po2 displayed on the handset, or he may have just heard the stuck solenoid, or noticed a rise in buoyancy.

How would you bailout from a dive like that?

If you have off board 80% or better and feel comfortable flying manually you may not need to bailout. If you need to bailout just ascend (the easiest way to drop po2) and/or do a diluent flush.

What would happen if the handset wasn't working, just count on the back-up handset?

The hand sets are just glorified oxygen analyzers. The importance of voting logic and independent readings means for ccr diving you need at least 3 o2 cells. The Inspiration has two independent readings of 3 cells one Master one Slave. If the slave revolts and kills the master the slave becomes the master. Most people would abort the dive upon the failure of one handset, but if it occurred during a dive/deco it would not be a catastrophic event.

Safe Diving,

Chuck Northrup
Going Under Dive Center