Charcoal is just about the worst thing you can burn in terms of fumes I believe, thats one I'd never use indoors including a tent because you realistically have no control over the burn. After Katrina there were quite a few deaths caused by people bringing charcoal BBQ's indoors....fumes, poor ventilation = death. Know your kit, make sure you have a good air flow and = warm camper
Again it's not the fumes, they died specifically of CO poisoning.
I am not going to bother answering the nit picking and bickering posts, i think Blimo has made some good points and my opinion is clear i believe.
I have cooked in a tent and chances are i will again, i do take precautions though and i do feel strongly that if we are advising people it's ok to cook in a tent then it's imperative that these precautions are made 100% clear.
With regards to having a candle or heat source in the tent.
Tents specifically designed for this purpose (teepee etc) aside i can't see any point in having a lit candle in atent.
It's heat output is insignificant and in this day and age torches last forever and are a LOT safer if it's illumination you want.
For me the risks simply do not outweigh any sort of usefulness.
For other heat sources again with modern materials i really don't see the point in the UK.
I've camped out in conditions where my urine disposal bag was frozen solid in the morning yet i was toasty warm all night tucked up in my sleeping bag.
I can see the draw of older simpler ways of doing things, but if this floats your boat your better off having a tarp or natural shelter next to a fire with a back block to focus the heat towards you.
I just can't envisage a case where i would risk having a open flame in my tent purely for heat generation, even if it keeps you warm for 30 mins or so only a fool would sleep with it lit so it offers no advantage during the night.
I didn't really want to get into all this bickering my intention was to clear up on some inaccurate posts and confusion.
I've made my points clear and i think it's obvious that i err on the side of caution.
The other side is this:
well you're still alive so is that not enough proof, did you feel ill?
If your adult you make your own risk assessment, if your a minor then please please please speak with someone face to face that knows what they are talking about before risking your life.