By the way, tea lights are pretty good too, provided you take the proper percautions.
Indeed!  For all you dataholics, a table of snow shelter temperatures I got from an old instructor shows:
Outside     Inside     Conditions
Temp (F)    Temp (F)
+4          +8         No door - unoccupied several hours
-2          +7         No door - unoccupied several hours
-7          +14        Canvas door - unoccupied
-14         +21        Unoccupied 2 hours - 1 candle - door
-14         +24        Half-hour occupied - 2 candles
-49         +20        1 occupant - no heat
-48         +23        2 occupants - 2 candles / 15 minutes
-55         +19        2 occupants - overnight - no heat
The only citation is "Scandinavian Airlines: Survival Manual"
Also, when using a chemical heat pack, optimum placement when sleeping is probably over the femoral artery.