Hard to design a system that can be operated by a chimp when the people actually designing and implementing the process are clearly incompetent.
If they don't have a medical professional monitoring the person's oxygen levels to ensure he is dying as fast as it is supposed to work, how will they know if their made up bullshit about it being humane when forced upon someone is accurate?
Imagine if they were putting a free diver or other person who has practiced holding their breath for extended periods of time, how would they know if it was even working without monitoring them?
The states that execute people have lied about every prior method being 'humane' and non of them ever were in practice on someone who did not want to die. The electric chair supposedly killed the person instantly, but that was a lie. Lethal injection was supposed to be putting someone to sleep and described in the same way as nitrogen, but that was clearly a lie in practice because the people that do it are incompetent.