Does radiating heat cross path with another radiating heat nicely? Suppose two radiators, each on a wall perpendicular to the other. Do the two radiations impair each other? 
 A: In an air-filled room, interference between individual photons from the radiators is irrelevant, as the radiation is rapidly absorbed by water in the air, and is homogenized by the Brownian motion of the air and water molecules. Therefore, the radiators do not significantly interfere with each other.
To intuitively see that this is true, we compare two radiators to two sound generators. Sound generators create pressure waves, which are alternating regions of positive and negative pressure. If a region of negative pressure from one sound generator overlaps with a region of positive pressure from another sound generator, the principle of superposition creates a region of static pressure (destructive interference).
Unlike sound generators, which can both pressurize and rarefy gas, radiators can only heat gas, and do not have the ability to cool down gas; radiation is either absorbed (in which case the gas gets hotter) or not (in which case the gas's temperature remains the same). Therefore, the cancellation that we see in the case of sound cannot happen here. 
