Traditionally, the only parameter used to measure the performance of total compartment (i.e. total flooding) water mist or water spray systems during fire testing has been the time to extinguishment. However, the use of a single parameter has been criticized since it can result in poor system designs. This study evaluates additional parameters in order to improve the characterization of system performance. Two series of fire tests were conducted with a number of water mist and water spray fire protection systems: the former in a 500 m3 test compartment using three different systems; the latter in a 250 m3 compartment using four different systems. The heat release rate of the fire and the gas temperatures inside the test compartment were measured. Based on these measurements, the fire suppression capability of the systems, their temperature reduction capability and their ability to mix water vapor, water droplets and combustion gases within the compartment were determined. The tests revealed that the time to extinguishment varies several tens of percent under identical conditions. It was also observed that the relative performance of the systems was influenced by the size of the fire. The results obtained with the additional parameters were much more repeatable and consistent than using time to extinguishment alone. It is concluded that fairly simple and inexpensive measurements can improve current fire test procedures.