The　extemporaneous　combustion　of　coal　remains　a　major　threat　to　safety　in　coal　mines　because　such　fire　accidents　result　in　casualties　and　significant　property　loss,　as　well　as　serious　environmental　pollution.　This　work　proposed　the　fabrication　of　flame-retardant　rigid　polyurethane　foam　(RPUF)　containing　expandable　graphite　as　char　expander/sealant　with　melamine　phosphosphate　and　2-carboxyethyl　(phenyl)phosphinic　acid　as　char　inducer　and　radical　trapping　agents.　The　as-prepared　RPUF　successfully　inhibited　coal　combustion　by　forming　thermally　stable　high　graphitic　content　expandable　intumescent　char　sealing　over　the　coal.　The　RPUF　achieved　UL-94　V-0　rating　in　addition　to　significant　reductions　in　peak　heat　release,　total　heat　release,　and　CO　and　CO2　yields.　The　external　and　the　internal　residual　char　structure　was　studied　by　X-ray　photoelectron　spectra,　Raman　spectroscopy,　and　real-time　Fourier　transform　infrared　spectra　techniques,　and　a　flame-retardant　mode　of　action　has　been　proposed.　This　work　provides　important　insight　into　a　facile　fabrication　of　highly　efficient　and　economical　flame-retardant　RPUF　to　inhibit　the　spontaneous　combustion　of　coal.　©　2019　by　the　authors.