Is there no CO2 danger from sleeping with gas stove on? Don’t people die from carbon monoxide poisoning from sleeping with open flames?
Outdoor fires well, are outdoors, so there's plenty of oxygen.
People die nearly every year in the brutal cold from getting desperate and bringing grills and such indoors to light, which is a big no no.
Otherwise - no, if there is enough oxygen coming in. When fireplace is done properly it is not a problem.