Cross Laminated Timber (CLT) panels are increasingly used for building construction; in specific cases, the indoor surface of the CLT panels is required to be “exposed”, thus making adequate fire protection of these elements a significant challenge. The main aim of this work is to experimentally determine the impactof an exposed CLT panel, in this case a ceiling, to the characteristics of a compartment fire. Experiments using either fire-resistant panels or a CLT exposed ceiling are performed in a test rig, corresponding to the 1/3 scale of the standard ISO 9705 compartment; a broad sensor network is installed to determine the main characteristics of the developing thermal-and flow-fields inside the compartment. In order to overcome certain limitations associated with achieving adequate levels of repeatability when a “realistic” time-dependent fire curve is used, a PID controller-based gas burner is employed; the ISO 834 standard temperature-time curve is used in all fire tests. The experimental results suggest that, as expected, when a CLT ceiling is used, the total fuel consumption at the burner is significantly lower. The thermal field inside the compartment exhibits certain differences, while the opening velocities were largely unaffected by the installation of the CLT ceiling.