Almost all patio heaters are infrared. The sun is a great example of an infrared heater. Its rays travel through space and don't heat it, but when it hits a solid object, Earth, heat is created. Infrared patio heaters don't try to heat the air (like a convection heater) but instead heat the furniture, floor, objects, and people directly. That said, in a covered area you will get some residual heat build up in the air.