This. Inhale from a helium balloon a couple of times, and you’ll get dizzy and pass out maybe 10 seconds after your second inhalation, having never felt an urge to gasp for fresh air. This works equally well with helium or nitrogen (or presumably any other inert gas, e.g. neon or argon). A bag over your head (and secured to your neck) with a steady stream of helium/nitrogen coming into it (or the bag prefilled with a large quantity of said gas) would reliably kill you, no pills required.
The first part of this statement is how Boston singer Bradley Delp did it. 
Helium and oxygen, abbreviated heliox, is sometimes used for hospitalized patients with COPD, and deep-sea divers too, because it’s lighter than room air or nitrogen, and people can inhale it more easily and in the case of divers is much less likely to cause “the bends” on ascent.
Revtim, I just wanted to say, if you haven’t you may wanna talk to your doctor. It sounds like you’re having laryngeal spasms. I have them too. Your throat closes when you try and inhale but you can exhale fine. They definitely make you panic but the key is to in fact relax and remain as calm as possible. Anxiety tightens them up even more, calm helps them to relax again. Not an easy thing, but when you know what’s going on it’s easier. Also, unless you’re on sedatives, the worst case scenario is that it will go on only long enough you pass out. The moment you’re unconscious, the muscles relax and you can breathe again.
If you even think that’s what these are, talk to your doctor FIRST. I am not intending to give out actual medical advice, just tips to help if that is what in fact they are
It takes several minutes usually to get to that point though. If it happens, do your best to relax and remain calm, sit or lie down on the floor (so if you do pass out you don’t fall over and hurt yourself) or if you’re driving pull over. If you’re diagnosed make sure your friends and family know so THEY don’t panic when it happens. Your in the most danger from them when they think you’re actually choking and try to heimlich. If I suddenly can’t breathe, my friends and family know to ask me first, ‘are you choking?’ and ‘do you need your inhaler’ (I’m asthmatic too). If I shake my head to both those questions, they know I’m having a spasm and it’ll pass. They can also tell others if we’re at a restaurant or something what it is and that I am not in fact choking.
Of course, that means when asked, you need to answer honestly regardless of your level of panic.
One more important thing, make sure if you ever have surgery, you tell your anesthesiologist you have these spasms. They are the most dangerous when you are under anesthesia and it’s one of the few times it can actually kill you. If an anesthesiologist is aware- and trust me, every single one out of school will know what you’re talking about- they will take extra precaution not to trip this action when inserting or removing any oxygen tubes. If they do trip it, they’ll know what to be keeping an eye out for and can respond immediately on the first spasm, rather than perhaps being distracted with the machine and not noticing the spasm is occurring.
So, that was a long rambling off topic post, but just thought I should let you know if you don’t already. There are also videos of what the spasms actually look like which can help your GP if they’re not familiar with them- mine wasn’t.
What happens Thursday?! :eek:
The special changes to lamb