The treatment of woollen blankets with dust-laying oils for the purpose of reducing dust-borne infection may be accomplished by the use of positively charged emulsions of oil in water. The chemical aspects of this process have been investigated and the influence of the various factors that affect the rate of exhaustion of the treating bath has been studied. It was found that the rate of exhaustion is increased by (a) raising the temperature, (b) raising the pH, and (c) reducing the concentration of emulsifying agent to the minimum amount necessary for stable emulsification of the oil. Traces of soap remaining in the wool after laundering cause a reversal of the electrical charge on the emulsion droplets and therefore prevent complete exhaustion of the treating bath. Suggestions are made regarding the practical application of the process.