My I suggest you invest in a Carbon Monoxide detector.....they look like a smoke alarm.........but they detect gas...instead of mounting them on ceiling you mount them at the lowest point in the van...as gas is heavier than air and sinks..
I don't have one of those (yet), because I did not realise they existed. But I agree with you 100%. Cheap life insurance. As they say, if it saves 1 life.
I installed one in my van.....Aust Day weekend....it activated.....I couldnt find any leaks.....I put it down to build up of fumes from glues and paint etc .......inside the van was over 45c at time and was closed up..at home