The present invention relates to methods of using at least one fluoroketone selected from monobromoperfluoroketones, monohydromonobromoperfluoroketones, (perfluoroalkoxy)monobromoperfluoroketones, (fluoroalkoxy)monobromoperfluoroketones, and monochloromonobromoperfluoroketones for i) extinguishing fire by applying to the fire such a fluoroketone, ii) preventing fire in an air-containing enclosed area containing combustible materials by introducing into the area such a fluoroketone and maintaining the fluoroketone in an amount sufficient to suppress combustion of combustible materials in the enclosed area, and iii) reducing or eliminating the flammability of a flammable working fluid, by mixing between about 0.1 to about 99 percent by weight of such a fluoroketone with the flammable working fluid.