The thermal decomposition of organophosphorus fire-retardant (OP1311) and/or organonanoclay (Cloisite 30B) is hereby investigated employing thermogravimetric analysis (TGA), to give an insight into their intrinsic behaviour and interaction in polymer nanocomposites for fire safety applications, because the addition of OP1311 and Cloisite 30B in Polyamide 6 (PA6) seems to have a synergistic effect on the thermal decomposition of PA6 (part 2 of the paper). An important objective of this research was to determine to what extent phosphorus components escape in the gaseous phase, which will affect the heat of combustion of the fire-retarded polymer. The decomposition products arising from pyrolysis and combustion are investigated by means of Fourier transform infrared spectroscopy. Under pyrolytic conditions, the inclusion of Cloisite 30B into OP1311 (FR) shows a synergistic effect on the initial mass loss at low temperature of similar to 280-420 degrees C and leads to the acceleration of the thermal degradation process. While the DTG curve of Cloisite 30B shows two distinct degradation peaks (steps) that of OP1311 and OP1311 plus Cloisite 30B show four degradation steps. TGA measurements of OP1311 in nitrogen show more mass loss than in air, whereas Cloisite 30B gives similar amounts of mass loss in air and nitrogen. In nitrogen, the major evolved gaseous species from Cloisite 30B alone are hydrocarbons, 2-(diethylamino)ethanol and water, whereas the evolved gases from that of OP1311 at similar to 320 degrees C are mainly water, at similar to 420 degrees C, carbon dioxide, water and ammonia and at 480-570 degrees C diethylphosphinic acid. Under thermo-oxidative conditions, the gases evolved are mainly carbon dioxide and water from both Cloisite 30B and OP1311. Copyright (C) 2009 John Wiley & Sons, Ltd.