In this work, we analyze different factors that may affect heat measurements, in a device, based on the optical beam deflection method (OBD). We demonstrate that it is possible to improve the heat limit of detection (HLOD) of the device by increasing its sensitivity using a proper cell or a proper monitoring phase. On the other hand, we prove experimentally that the gradient of the refraction index is almost vertical, so it is possible to apply a theoretical model based on one-dimensional heat propagation to predict the temporal behavior and the magnitude of the deflection beam. (C) 2003 Elsevier B.V. All rights reserved.