A domestic heating fuel composition, comprising (a) a paraffinic hydrocarbon composition comprising at least 90 wt % normal paraffins and/or iso-paraffins comprising from 6 to 24 carbon atoms, wherein the weight ratio of iso-paraffins to normal-paraffins is below 6 to 1, and (b) at least one compound having a C/H molar ratio of above 0.8 and soluble in component (a) at ambient conditions, wherein the component (b) is present in the fuel composition in an amount effective to increase the responsiveness of a yellow/red flame detector to a required threshold level.