This paper introduces an improved approach for selecting the location of Radio Frequency (RF) sensors used for detecting objects in a building. Given the building map and materials, a number of moving or static objects carrying RF tags are to be detected in a building in an emergency situation. Liu et al. (2005) presented two algorithms that can be used to compute the number and deployment locations of sensors and detect objects using the data from the deployed sensors. However, their first algorithm only accounts for absolute deployment cost. It can be greatly enhanced by using relative deployment costs. By comparing the results of the simulation of the existing and improved algorithms using MatLabTM/C++, this work concludes that when determining the locations to deploy sensors, one must take into account the locations relative to the locations of sensors already deployed. The results can be used by first responders such as police and firemen in detecting their indoor crews in the event of fire and other emergency situations.