The P1SS™

complete unit & owner (5.39 kB)

The finished unit.



mouthpiece (14.2 kB)

Modified power inflator (original shown on the left) with bayonet off/off knob (detailed view right) to isolate mouthpiece and manual direct feed from oxygen cylinder. Adding O2 here means that any CO2 in the dead space between the mouthpiece and scrubber should get blown into the scrubber.

O2 Supply

first stage (9.38 kB)

Oxygen-clean Poseidon Cyclon 300 first stage with "button" type Apeks pressure guage. It is not meant to be accurate (and it isn't) just to tell you that you have enough O2 - an overpressure relief valve would be a GOOD THING to add.


scrubber cannister assembled (9.55 kB)

Scrubber cannister assembled - it is made of of 6" OD polyolefin gas pipe (5" ID) with end caps held down by latches.

scrubber cannister apart (8.68 kB)

Scrubber cannister apart - the end caps are fitted with slightly recessed O-rings to provide a water-tight seal. The holes for the end fittings are threaded to accept the 22mm tank connectors.

end fittings - components (9.16 kB)

End fittings components - obtained from the rebreather section of my local hardware store.

end fittings - components (7.15 kB)

Assembled end fitting - the pipe comes with guide marks for cutting. Enough pipe is left exposed to provide a good seal for the hoses which are standard breathing hoses from a BC. Note the reinforcing insert around the end of the pipe.

filter (7.15 kB)

Filter material to surround scrubber is made from discs of household scouring pad. It is so cheap that it is disposible.

diffuser (7.15 kB)

A polyolefin heavy-duty door mat makes an excellent diffuser to get good gas flow thorugh the scrubber bed. The bristles also act as springs to compress the scrubber material.

filling (29.1 kB)

Sequence showing filling of scrubber cannister with Sofnolime (about 2.5 lbs/1 kg) - the diffuser and filter are put in the bottom first (in this order). Duration - over an hour though I change it after 60 minutes use. If you want to travel abroad with Sofnolime, it is a GOOD IDEA to take the Materials Safety Data Sheet with you - a suitable version is available here.

clip lock (9.65 kB)

It is a good idea to wire down the latches to stop the end caps falling off.


back to BC (29.2 kB)

Replacing the scrubber cannister with a through connector can turn the P1SS™ back into a BC or for ease of transport.

end stop (4.06 kB)

Capping the scrubber cannister also aids transport.


finished device (28.5 kB)

All assembled with on-board O2 supply.

Last updated 28 March 2010 by Duncan Priceback