Well, I was only considering electrical ones since we have an all electric house and see no use in adding something gas since it kind of negates the safety of our all electric home. Do electrics give off CO2?
The oil filled ones to which I was referring, in case thast is what you were thinking, are the type that are in a sealed thing that looks like a radiator. From what I understand, electricity heats it up inside and it then heats the oil which radiates into the space. It is supposedly safe and efficient but I don't know anyone who uses one currently.
We thought about baseboard ones as well, that is part of what I was asking, since they were referred to as space heaters as well. Our main thought with those was whether the ones that can run off 120 current would be fine. We really don't see needing to use our space heating very often, just in cases where visitors might feel a bit more comfortable.