A detailed HGMF investigation has been carried out on filtration efficiency using a matrix of rectangular AISI 430 stainless steel wool to filter basic oxygen furnace dust. Filtration efficiences of 99% and greater can be achieved for submicron particles down to an optically measurable 0.24 μm diameter; for particles of 1 μm and above, filtration efficiencies are indistinguishable from 100%. Varying only one parameter at a time has isolated the effect of volume packing fraction (wire interference), field strength, gas velocity, filter length and wire size and aspect ratio, which are reported. A total-matrix penetration equation for rectangular wires was derived. Using this equation, values of dimensionless capture radius were obtained and plotted against the Stokes numbers.