The panic/choking feeling comes from a buildup of CO2 in the air and body, not lack of oxygen. We know from experiments/accidents that when CO2 saturation does not happen, people don't feel like they are choking or can't breath even if they are not getting any oxygen.
Right. Humans don't have a blood oxygen sensing system; you can be trained to recognise the signs of hypoxia (as divers, military pilots, and astronauts are), but there's no physiological alarm for it.
This has resulted in many accidental recreational and commercial deaths, where e.g. divers hyperventilate beforehand to extend their time underwater (purging more CO2, so they can stave off that chest-crushing feeling of needing to breathe right now) which leads to blackout and drowning because you ran out of oxygen before the high blood CO2 sensing kicked in, or someone walking into an inert gas storage tank to perform maintenance (mistakenly believing that it had been purged), and just dropping on the spot and asphyxiating with no warning.
Some comments mentioned that some people who attempted to use nitrogen had problems. According to the Wikipedia a fast switch to breathing a nitrogen and no oxygen atmosphere has "no symptoms at all", but when it happens slowly what happens to people varies:
> a slow decrease in oxygen breathing gas content has effects which are quite variable.[5] By contrast, suddenly breathing pure inert gas causes oxygen levels in the blood to fall precipitously, and may lead to unconsciousness in only a few breaths, with no symptoms at all.[3]
They cite scuba diving rebreather accidents as one source for experiences. I think there should be people to tell the tale if they got rescued, "never dive alone", after all, and ships for divers should be equipped for emergencies. I guess other than observation of someone committing suicide with this method we may actually have personal experience stories.
I looked into this when I had a huge health scare that changed my life (it "only" was heavy metal poisoning and after lots of chelators I'm doing very well, better than before), and nitrogen was what I considered because I saw a chance to actually get my hands on some, compared to drugs. Bad thoughts, but I'll still keep it in mind in case I ever need it. Living through all the heavy metal issues was bad enough but at least I had hope. If it's similar or worse problems or even pain with no hope I don't want to have to endure.
I’m amazed the author of the article was able to determine this. May they rest in peace.