An important problem with sensor networks is that they do not provide information about the regions that are not covered by their sensors. If the sensors in a network are static, then the Alexander Duality Theorem from classic algebraic topology is sufficient to determine the coverage of a network. However, in many networks the nodes change position over time. In the case of dynamic sensor networks, we consider the covered and uncovered regions as parametrized spaces with respect to time. I will discuss parametrized homology, a variant of zigzag persistent homology, which measures how the homology of the level sets of a space changes as the parameter varies. I will show also how we can extend the Alexander Duality theorem to the setting of parametrized homology.