sleeping with generator on

I wonder how many of those CO deaths were due to propane heaters running inside the coach (likely most) and how many were due to generator exhaust (likely few) and how many were due to some other CO source.
Not knowing the answer to any of these makes the statement that "as many as 500 people die each year" a completely random statement that may or may not have anything at all to do with "proper" generator operation.