The description of experimental plant for a generation of free concentrated thermal vortices has been presented. Heat rates have been revealed also spatio-temporal field of temperatures due to unstable stratification results in appearance of free vortices has been measured. The possibility of investigation of free concentrated vortices dynamics with usage of video filming and different visualization methods has been demonstrated. Problems of formation and extension of inner cavity of free air vortices have been investigated. Transient velocity fields in cross-section of free vortex structure have been found.