where HRRav is the heat release rate averaged over 30 seconds (in kW), SPRav is the smoke production rate averaged over 60 seconds (in m2/s), and t is the time elapsed after the beginning of the test (in s), i.e. the ignition of the burner. The units of FIGRA and SMOGRA are W/s and m2/s2, respectively. Constant coefficients are added to the definition of the parameters to obtain convenient ranges of numbers. Different heat release related threshold values for the FIGRA calculation are used in different classes to obtain FIGRA0,2MJ and FIGRA0,4MJ values. Also