What are the primary gases produced by propane combustion?
Like any hydrocarbon, propane when completely burned produces carbon dioxide and water; these are not too bad, although you could use up enough oxygen and produce enough carbon dioxide to suffocate anyone in the building. Complete combustion never happens in the real world, and so you end up with partial combustion products of which the worst is carbon monoxide, which combines readily with the hemoglobin in the blood, displacing oxygen and suffocating the victim from the inside. This is how people die in fires, from car exhaust, and so on. Using outdoor heaters indoors is never a good idea, even if the building seems adequately ventilated. There have even been cases of carbon monoxide poisoning in open ski boats on the lake.
