yeah, if he is producing CO2 faster than the suitcase can exchange it with fresh air from outside, the CO2 levels will build up very quickly until he dies from CO2 toxicity, which happens at 4% to 6% air volume, and you exhale 4%, so being confined in a small space like that, you'll use up your air and start to get toxicity in a matter of minutes.

There was probably enough air exchange that it took him hours to die given that she left him that way overnight and apparently filmed 2 videos hours apart with him begging to be let out.

yeah, if he is producing CO2 faster than the suitcase can exchange it with fresh air from outside, the CO2 levels will build up very quickly until he dies from CO2 toxicity, which happens at 4% to 6% air volume, and you exhale 4%, so being confined in a small space like that, you'll use up your air and start to get toxicity in a matter of minutes.