Oil-free heaters are better than oil-filled heaters because they heat up more rapidly, cool down more quickly and are easier to transport. Some oil-free heaters also produce an orange or red glow that makes it easy to see when the heater is too hot to touch. The most effective and powerful oil-free heaters combine intense heat with a fan system that spreads hot air throughout the room.
The most popular oil-free heaters are halogen heaters, which have metal heating elements and a reflective silver backing that directs and focuses the heat. About.com expert Timothy Thiele explains that compared to oil-filled heaters, halogen heaters provide much more direct heat and are more effective in drafty spaces with no insulation.
Halogen heaters are also the best choice for outdoor use because they generate a stream of intense, directed heat. Oil-filled convection heaters radiate heat from all sides, gradually warming the surrounding air. This makes them ineffective in environments that do not retain this radiant heat.
Halogen heaters belong to the infrared heater family. Infrared heaters produce heat within two seconds and have higher maximum temperatures than oil-filled models. Many infrared heater styles have applications outside of space heating. These include shrinking industrial plastics, heat treating glass products, warming food and hardening chemical coatings. Infrared heaters are also indispensable in zoos and veterinary hospitals, where they heat reptile habitats and keep premature mammalian babies comfortably warm.