The TEVO Heater uses infrared light to transfer warmth from the bulb to whatever surface it lands on. For maximum efficiency, the light is concentrated in a zone by the reflector rather than spraying out in all directions. The closer to the bulb you are the greater the warmth you will feel. Like the headlights of a car the light thrown out is a flattened cone shape and fades at the edges. If using your Heater in an Outdoor setting using 2 Heaters will give more comfort if the area heated is effectively in the crossfire thus warming people front and back or left and right. Any increase in breeze will cause you to cool down (wind chill factor)  even though the heat received from the Heaters will remain the same.