The ceramic cube heaters are probably the safest of all the forced air type portable space heaters, and I’m kind of partial to them. I wouldn’t use any type of electric heater in an RV that uses resistance wires or quartz tubes that glow red hot.
The heating element in a ceramic heater is a positive temperature coefficient thermistor (PTC) which is self-regulating. If the air flow is restricted, the PTC increases its resistance to reduce the power input and limit the temperature output. You can actually hook one of these heaters to a Killawatt meter, block the air flow and watch the power drop off. Try it and see. A ceramic heater will not get hot enough to ignite flammable materials.
It seems like most of the ceramic heaters nowadays have overtemp and tip over protection on them, but I have 2-3 older ones at home that only have overtemp protection.
:):)