Thought this was interesting... Polar Challenge FAQs

From the FAQ:

What about in the tents?

At the end of a day when you are tucked up in your tent and swapping
stories about the different types of ice you have seen, you will have
your stove on; this can keep the tent quite balmy, however the
temperature drops very quickly once the stoves are off. The nippiest
time is when you awake and the opening to your sleeping bag (which is
great while you are in it) is covered in ice from where your breath
has frozen. If you sleep in the buff, when it's your turn to get the
stoves going it can be a bit bracing, particularly if the stove is so
cold it needs putting in your sleeping bag to warm up to an
operational temperature.


They also address the dangers of having a stove in a tent, then:

But every aspect of the arctic is potentially dangerous. It all comes
down to good personal admin or "knowing where you put things and not
knocking things over". If you don't heat your tent up you core body
temperature will drop and as you sleep you will become colder and
colder, hypothermia can soon set in.