I have evaluated alternative suicide methods with CO2 such as dry ice and even using a fire extinguisher with CO2 but the first is impractical because it tends to sublimate and given my hesitation it would end up all sublimate before I decide to do something while fire extinguishers are too expensive and I don't know how to explain it to my parents, of course I could say it's for fires, in the end it wouldn't even be that suspicious but I don't know if the amount of CO2 inside would be enough for a small room, spraying it inside the passenger compartment of a car I don't know because it tends to lower the temperature quite a bit and I wouldn't want the cold to become unbearable and the SI to make me run away.
I would say that the method in this thread is the better with CO2.