Baked beaners

Well, that answers my immediate question of how you had a medical emergency involving a dozen people on a freight train.

I think heat stroke is more likely in that timeframe.

Presuming all/most of them were hospitalised as a precaution, I don't think those containers are airtight enough that 12 people can make the air unbreathable that quick, if ever, but maybe they are. They have vents built in usually.

But hours and hours in a metal box in Texas sun, I bet that'll cook you.