The heat of formation of the fire suppressant, 2-H Heptafluoropropane, which is a replacement for ozone depleting halons, ΔH f, 298 K(CF 3CHFCF 3), has been calculated at the B3LYP, MP2 and CCSD(T) levels with basis sets of up to cc-pVQZ quality, and with the model chemistry methods: G2(MP2), G2, G3 and CBS-Q, employing three reaction schemes. The CBS limit value of -370.6 ± 2.3 kcal/mol obtained is believed to be the most reliable value currently available. This is recommended to be used in thermochemical/kinetic modelling of the inhibition chemistry of CF 3CHFCF 3 in flames. ; Department of Building Services Engineering