I used to ice-fish a lot...hundreds of days spent sitting in a small portable shelter with a propane heater running. I used about 4 different heaters in that time. I had some friends who used lanterns. We worked very hard to seal our shelters from winds and drafts...imagine below-zero temps and gusty winds. Our shelters all had snow-skirts and we would use shovels to pile snow on them to the point that no air could slip in. I was always wary of heater malfunctions, but in all the time (decades) I spent doing it (with hundreds of other guys out there on big ice) there was never an incident of CO poisoning or heater/lantern-related death. Don't misunderstand me: I never assume anything isn't possible. I'm simply relating what I've seen. One day I lit my heater and it turned into a fireball inside my shelter. I basically uprooted the shelter and kicked the heater away from me...watched it burn to a crispy hunk of blackened metal. I'm far more wary of fires in shelters than I am CO poisoning or O2 deficit. That's why I basically won't go to sleep with a fire or heater burning in a shelter. The odds are against injury, but the odds are high that any injury would be very serious or fatal. Anyway...the only source of heat I would use in a shelter is a woodstove which vents to the outside. Propane heaters and lanterns don't vent outside and any malfunction means potential CO exposure. Incidentally, I've been told a couple times that the catalytic heaters are far more likely to produce noxious or dangerous emissions (vs a lantern) and I believe that. I've been doing some searches looking for evidence of O2 deprivation in tents (the usual camping-type tents) and I can't find any proof of it related to the tent being sealed too well. I do see some evidence of CO poisoning (which actually causes hypoxia by displacing O2 in hemoglobin) when combustion byproducts are excessive and build up within. Fortunately those situations tend to only happen when a heat source malfunctions and not in normal operation. From a CO emissions perspective I believe a woodstove is basically as safe as it gets.
"I had BearPaw add a silnylon 18" width sod cloth + tie-ups to my SL5 in 2013. The price was $95 and $25 for shipping and insurance. The weight increase was 11.3 oz. The quality was high and the turnaround was only a few weeks. The integrated tie-up straps allow me to roll and raise any portion of the sod skirt I want up for ventilation."
Exactly what I have in mind, with the exception of making the skirt around 10" wide. The tie-ups are the only way to go.
