The TEM chamber is a proposed exposure device for experiments detecting cell responses to electromagnetic irradiation at the mobile frequency of 900 MHz. In this paper, we extend the traditional propagating-wave exposure to the standing-wave exposure. Four standing waves with different properties are produced respectively by two types of passive loads and two types of active loads. Systematically, the maximum E field and maximum H field of the standing waves are used to expose Petri dishes of three sizes. The standard deviation (SD) of the specific absorption rate (SAR) is calculated for the cell layer and the cell suspension. We compare the SD data to determine the best arrangement with the highest exposure uniformity while considering the exposure intensity. The investigation uses the numerical simulation of the finite-difference time-domain (FDTD) method with the result accuracy supported by comparison to theoretical data on the field distribution in the TEM chamber.