Last weekend I spent a night in an igloo. The event was organised by professionals (it was a company retreat) and during the night there was always one of the guides awake making rounds and checking on the people in the igloos. They also made sure that the entrances stayed clear (there was some heavy snow fall).
For Oxygen the method the guides used was to put a small candle inside every igloo: their reasoning being that should the candle go out the people in the igloo would have to be evacuated because the Oxygen was getting low (so that was what they were checking on regularly).
I was wondering:
- How real is the danger of suffocating in an igloo with an open entrance, but without air holes in the cupola?
- How real is the danger of suffocating should the entrance (and any potential air holes) be covered by heavy snow fall in the night?
I'd be interested in an estimate of how much time can pass before you should start to be worried...
And maybe as a follow up:
- How often would one have to check for clear entrance / air holes in case where there is no person staying up all night?
Let's assume an igloo for 3 people (maybe 2m diameter), built with a 'siphon' style entrance of maybe 50cm diameter (i.e. the entrance makes a bend that is the lowest point of the igloo, thus trapping the warm air inside).