Mass concentration means mass per unit volume and is used in the construction mass_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. The chemical formula for halo2402 is C2Br2F4. The IUPAC name for halon2402 is 1,2-dibromo-1,1,2,2-tetrafluoro-ethane.