I got this from Mountain High who saw this thread:
On the O2D2, the reason for the marking is that if the “non pilot” outlet has nobody breathing from it, it doesn’t keep beeping to warn you. Otherwise, an O2D2 could never be used by just one person. If you fly alone, you have to use the “pilot” outlet and then you get the beeping if you stop breathing.
That way, if you die, your passengers find out quickly 
Thanks…is there any technical / practical difference between the passenger outlets and the pilot outlet? I notice even on the O2D2 it indicates one outlet for the pilot
A lot of people who have fitted oxygen systems (typically in turbo aircraft) use the O2D2 to save gas, but I think most need a stepdown pressure regulator in front of each O2D2 (or O2D1) because the aircraft’s 1st stage reg outputs too high a pressure for the O2D2 regulator.
I am using an inline reducing regulator to connect to the O2 connection panel overhead in the Cirrus. That inline regulator goes to the O2D2 and from there you have the Oxyarm. Only drawback of this new Oxyarm version is that the tube is rather short, so you might have to extend it (the tube from the O2D2 to your headset.
Hi Sjoerd, so you have details on which bits of kit you use to connect it all together? ie built-in O2 to O2D2 to Oxyarm….I have a built-in system on my Mooney with 115cuft bottle with altitude compensating regulator….with Scott connectors (3 in the back for passengers and 1 for the pilot up front)
Hodja: you might have noticed that my wife is also using the Oxyarm. I agree with you that it is a great setup and the O2D2 (or similar O2D1) pulse regulator is essential in not getting a dried out nose as well as in giving you an “ever lasting” oxygen supply out of a relatively small botthe. Without the pulse regulator, even a rather large O2 bottle will be empty in just 1 or 2 flights.
On the strength of Peter’s CFFC048 cylinder + O2D2 review, I recently bought those for my DA42-VI.
I completed the setup by getting a set of Oxyarms. Works absolutely excellent. I get 95% saturation at FL180 & hardly even notice I’m wearing the Oxyarms. Having the Oxyarm fixed onto the headset also makes for a very “streamlined” in-cockpit setup, as the oxygen tubes can be attached to the headset cable.
Also a full cylinder last almost 35hrs of use, single pilot. Great setup.
ploucandco: I will get you the details by mail later this weekend. Got your mail.
Aeroplus, I am interested in your O2D1. Sent you an e-mail.
