I don't know, somebody did the maths, maybe you could check with them to help people thinking of it? Supposedly CA is OTC at pharmacies (never got it myself), easier than SN, etc.
I am pursuing this not for myself but because currently there is someone who doesn't have other resources and is trying to get this right.
The math isn't the problem, it's the lack of proper equipment and training. It's one thing to create a bunch of CO2 and use a tube to get it into an upside down container. You can even make it airtight by submerging the bottom in some water in a sink or bathtub. Then what? You didn't have a vacuum pump to clear the air out of the container in the first place, so now you have a volume of gas that's higher pressure than the atmosphere (in addition to having a bunch of oxygen in there), so as soon as you move it, your CO2 is going to rush out, air is going to rush in, and since your partial gas pressure with CO2 and atmosphere is pretty close to 0, the CO2 gas in the container is going to rapidly move to an equilibrium with air of virtually no CO2. Jam your head into it real quick, problem gets worse - your head will drag in atmosphere, forcing out CO2, and you don't have a low enough O2 concentration to pass out quickly, the hypercapnic response triggers, it's painful, and you end up clawing at (and probably tearing or dislodging) your bag.
I'm not pointing all this out to be unhelpful, but there are a lot of very smart medical doctors who've given the question of how to die peacefully a lot of thought. They've written books, founded right-to-die organizations and made recommendations about the best ways for people who want to die to kill themselves. None of them recommend household chemicals because it's hard and painful. The only "household" method that's any good is carotid artery compression in one way or another. If you want to get out, and you only have access to stuff around the house, that's the way to go. Make sure you have half an hour's privacy at least, cut off blood flow to your brain and wait. Anything else is going to be painful, unreliable, or both.
Thank you for your response. Unfortunately due to pain I'm mind I can't hide my mood. But maybe I'll look into other methods like jumping somewhere.
Been there, done that. (Arguably, am there now). In my experience, you don't have to hide your mood. In fact, faking like everything is suddenly alright is a major red flag for suicide, so don't do that.
You're depressed, life sucks, you're "not sure life is worth living", but trying to commit suicide just made it worse. You need time, and a bit of space to get better. Admit it, let it show, and as long as you can hold back the "I'm still trying to kill myself" bit, you'll get some space and people will worry less and let their guard down, in my experience. Probably, they'll try to get you mental health assistance, maybe it will even help. If it doesn't, you've got enough space and bought yourself enough time to CtB "right".