Fan heaters are actually types of space heaters. The difference lies in their mode of operation: whereas a fan heater warms up the air and propels it using a fan throughout the area, a space heater may use a fan or warm the surrounding by radiation.
Space heaters are mainly used to heat up enclosed areas, and they work by either convection or radiation. Convective space heaters heat up the air, which in turn warms the surrounding people and objects, and a good example, is the fan heater. Convective heaters may also be fan-less, which makes them silent, but they still warm the entire space through convection. These kinds of heaters are most efficient in a well-insulated room.
Radiative heaters function by working in the infrared spectrum. They use radiant energy to warm up the objects in the nearby surrounding, and this heat doesn’t raise the air temperature. Radiant heat is directly absorbed by the objects and the skin, and makes these heaters work best in poorly insulated environments. A good example of a radiative heater is the halogen heater, which uses tungsten filaments.
Space heaters can easily cause a fire hazard and need to be operated with the necessary safety precautions put into place.