Did a dive on Hollis Explorer today

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How would it react if you added offboard O2 via a needle-valve?

I guess it would stop injecting as long as the PO2 was high enough. And if you close the needle-valve, it would resume injecting as the PO2 comes down again.

That would make it a mCCR/eSCR-clone, that I think would give you the best of both worlds, and very few of the cons.
 
The unit is very "sensitive" about alarms. My guess, it would alarm if there was no PO2 change after a minute.

Daru
 
Apparently, setting the DCP on manual and adding a manual valve to inject O2, some folks are diving it as a e/mCCR.... i'm still trying to find out more about it...
 
The net result of adding offboard gas, be it O2 or Nitrox, is to fool the unit into thinking you have not created as much CO2. The unit assumes that the O2 in the onboard tank is what you have available for metabolism. As you metabolize that O2 you create measurable amount of CO2 and therefore you have a calculable duration for your scrubber. If you bypass the onboard cylinder you are bypassing the pressure monitoring that informs the computer as to the amount of O2 that is used in the calculation. These are the volume calculations that yield the CO2 for fixation. There are other factors in the scrubber duration calculations and eventually they will determine the "filter" time that remains and is displayed on the status screen. The fact that you are deceiving the computer with this method forces the computer to yield somewhat inaccurate information regarding the usage parameters set by the manufacturer. That is your choice, but you damn well better know what the hell you are doing if you want to avoid injury. At this level of off-standard usage, the optional CO2 sensor is an ABSOLUTE necessity. If you are going to push the absorbent farther than you were instructed, you must have the CO2 sensor installed. Doing any of this is at YOUR OWN RISK.
As far as the actual content of the loop, the O2 sensors do track PO2 and therefore provide data regarding decompression/NDL limits accurately as long as the only two gases are O2 and N2.
There are a few of us that have pushed the limits of the Explorer, but we understand that what we are doing is for our knowledge and understanding. If you wanted a full trimix/100m eCCR and bought an Explorer, you made a mistake. That being said, I have both, I instruct for both and love to tinker. The Explorer is a fantastic unit when used within the manufactures specifications
 
There are a few of us that have pushed the limits of the Explorer

Can you elaborate ?? Have you gone past the limits or "discovered a unique application" or ? Not looking for a hack or a shortcut or a workaround. Just curious :)
 
SCR has a largish tank of gas that's theoretically breathable at any point in the dive rather than separate bottles of dil and 100% O2...coupled with the Explorer's standard BOV, one can theoretically dispense with separate BO bottle. Though if you somehow managed to get a caustic cocktail out of an extendair cartridge, I imagine you'd like to rinse thoroughly after hitting the BOV lever.
 
SCR has a largish tank of gas that's theoretically breathable at any point in the dive rather than separate bottles of dil and 100% O2...coupled with the Explorer's standard BOV, one can theoretically dispense with separate BO bottle. Though if you somehow managed to get a caustic cocktail out of an extendair cartridge, I imagine you'd like to rinse thoroughly after hitting the BOV lever.

Extendair cartridge in an Explorer ?? I'm intrigued :)
 
Extendair cartridge in an Explorer ?? I'm intrigued :)

Oh Gods...I just assumed anything that Fisher Price-y had to avoid making scrubber packing the diver's responsibility. That's...just fantastic.
 
SCR has a largish tank of gas that's theoretically breathable at any point in the dive rather than separate bottles of dil and 100% O2...coupled with the Explorer's standard BOV, one can theoretically dispense with separate BO bottle. Though if you somehow managed to get a caustic cocktail out of an extendair cartridge, I imagine you'd like to rinse thoroughly after hitting the BOV lever.

I am sorry, since I am not a rebreather dive, I want to understand this a little more.

If the gas in this rebreather can be breathed at any depth of the dive, how can the rebreather maintain a constant PPO2? Say you plan to dive to 100ft, you carry 32% (assume 1.3). At 100ft, it is 1.3, but at say 50ft, how can you get 1.3 out of 32%?
 
https://www.shearwater.com/products/peregrine/

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