Last time out I spent about 14 hours in my 3 man insulated popup hub. We were dressed in bibs so till close to morning we got by on the low setting of my mr heater burner. I had the ventilation openings on both ends of the roof open and at times I felt like i maybe had mild symptoms of carbon monoxide so I opened the triangle window from the top about 3 or 4 inches on the upwind and downwind sides. I worried if I opened the windows much more we would have to turn the heater up more and be pumping even more fumes out. Now that Im home Im wondering if i should have propped open a hole under one side of the floor to get it to draft up some from the bottom but wonder if that would make it feel more drafty in the shelter. So I was wondering how most of You handle the ventilation in a popup so you don't have to worry about kicking the bucket.