How would someone fail chorchoal method? The only way is if they don't enough chorchoal for the space or someone save you right?
I am answering this so that you don't end up brain damaged for life, not because I wish for you to die.
These are the ways to fail:
1. Leaving charcoal in chimney starter for too long (more than 20/25 mins)
2. Putting charcoal in the space before it has turned entirely white and cool
3. Not sealing the space properly
4. Not using enough charcoal
5. Using poor quality charcoal
6. Using a space that is not small
7. Not disabling smoke / CO alarms, if they are too close-by
8. Being discovered before at least 8 to 10 hours
9. Letting the CO build and then entering later, meaning CO is lost, & the high CO may shock the body
10. Not using heat mats / bricks , etcetera , to put the container of coals on . To prevent fire .
However, I wish that you do not attempt but seek solutions to your issues.