Pseudo one-dimensional mathematical models have been developed to compute plume width and centerline velocity and temperature in the plumes above finite size line and circular fire sources. The fundamental transient equations of mass, momentum and energy have been simplified by integrating them across the plume, using Gaussian profile shape assumption. The model equations have been solved numerically as we11 as analytically for different values of source Froude number (Frs). Explicit relations have also been derived to compute centerline velocity and temperature in the plume.