Having recently attempted to use this device. I must say I do NOT recommend this method. Also note I have recently been ambivalent about taking my life, and I realize that may play a part in my perspective.
Air tight seal: Achieving this is next to impossible. You can get a fairly good seal with the mask and head straps, but once your body begins doing things on its own its much harder. A forceful expulsion on air from your mouth can be sufficient to break the seal. Also if you begin to perspire that might also affect it?
Connections: They are simple plastic and pvc connections, just a male/female connection system, they disconnect easily as there is no latch or screwing mechanism to keep them in place. In order for it to not disconnect, you would need to lie extremely still.
The Lung: I'm not sure of the actual name. I am referring to the plastic bag inside the cardboard box functions as the devices 'air supply'. This is far too small. It makes your breathing feel labored and pressured. A sense of anxiety and hyperventilation sets in. It is not comfortable.
The Canisters: These are meant to scrub the C02 out of the returning air. They may have been working, but the shallowness of the lung was enough to cause panic in the first place.
I tried multiple times. In all attempts the anxiety/ panic of not getting enough air set in very quickly nor did I ever reach a point where I felt like I would pass out, let alone getting light headed.