Collective Protection (ColPro) enclosures are designed to prevent exposure of personnel to CBR materials. In the event that particle phase materials enter the enclosure, through entrainment or by release from contaminated equipment or clothing, there is the potential for occupants to become exposed. Concepts for the reduction of the risk from such hazards include the use of biocidal coatings on the enclosure surfaces. The purpose of this work has been to extend, test and apply models of aerosol transport and deposition within enclosed spaces to estimate the fraction of aerosolised particles that are likely to deposit on internal surfaces. This information has been used to provide an assessment of the potential benefit of biocidal surfaces.