Found This Helpful. Comstock/Comstock/Getty Images. Temperature can affect both the structure of a molecule and how it interacts with surrounding molecules. Heating some molecules, particularly large, biological molecules such as proteins or nucleic acids, will cause them to change shape or even to break up.
The air comes through the diffusers in much larger velocities and different temperatures than the ones tolerated in the space. Due to diffusion, the velocity and the temperature differences are gradually decreased until they reach the tolerable limits.
The concentration and the molecular weight of the inhibitory compound affect the size of the zone of inhibition (compounds with a low molecular weight will diffuse farther from the disc more rapidly). The purpose of the control is to check for the effects of any variables other than those being tested.