Sorry but the chance of CO poisoning from candles if nearly zero, They are burning very slowly, well controlled and unstably. They produce very small amounts of CO and will go out quickly if oxygen levels drop. Nearly anywhere is adequately ventilated for candle use. Thats not to say its super clean though as there will be soot, unbunt wax etc in the fumes but thats a different argument.
This is where confusion starts, if you do not know 100% what your talking about then with opinions related to peoples safety it really is best to just not say anything.
AGAIN
If you have a candle burning in a poorly ventilated environment, it will consume the oxygen until there is very little left.
Once it gets to this stage it will start forming CO, leave it unventilated much longer and you will fall to sleep and never wake up.
You have to remember it's not JUST the candle that's consuming oxygen, you are as well.
IT PRODUCES CO ONCE THE OXYGEN LEVEL DROPS.
It's NOT the type of heat it's 100% down to ventilation, even burning incense in a poorly ventilated room can cause CO poisoning.
If you are in a well ventilated or large room of course there is a very small risk from a candle.
If on the other hand you are in a small shelter that's poorly ventilated then it's VERY dangerous.
I'll also repeat again THE CANDLE WILL NOT GO OUT IF THE CO LEVEL IS HIGH.
Please stop confusing what is a very very simple matter, if you have questions ask, but if you don't understand please do not express a poorly researched opinion.
You have to remember it's not just the candle that's consuming oxygen, it's you as well.