Mid-infrared (IR) orbiting platforms are attractive candidates for monitoring fire on a global basis, as needed for global biogeochemical studies. In the mid IR, fires radiate intensely against a low-energy background. Thus fires occupying a fraction of a percent of a pixel can be detected. Fire size and temperature can, in theory, be calculated from multi-channel IR measurements. The fire record in raw IR data is biased by obscuration by clouds and smoke, sensor saturation, difficulties in gaining a representative sample given the diurnal variation in fire activity and the large role played in global fire emissions by cooking fires, charcoal making and very small burns on agricultural wastes. The bias is spatially variant and its nature is poorly understood. Further research and engineering is required before IR sensing can improve upon current rough estimates of biomass burning based on scattered available data.