AbstractTo reduce the incidence of fires in coal‐mines, the British National Coal Board (NCB) has requested a fire‐resistant grease which would be used in conveyor idler bearings and which would give the performance of good mineral oil‐based greases. A candidate grease was produced by the authors' company, based on phosphate ester, which is under field test by the NCB and running satisfactorily after one year. The results are encouraging so that consideration is being given to use of this type of grease in other applica